Fixes typo in word "failed".

Fixes bug where incorrect error is printed. The old code would only
ever print a nil error, instead of the validationErr which is being
created.

Fix some connect connect validation

`admissionValidators` doesn't aggregate errors correctly, as it
aggregates errors in `errs` reference yet it always returns the nil
`err`.

Here, we avoid shadowing `err`, and move variable declarations to where
they are used.

`groupConnectHook` assumes that Networks is a non-empty slice, but TG
hasn't been validated yet and validation may depend on mutation results.
As such, we do basic check here before dereferencing network slice
elements.

Ensure that we're reusing the base configuration between client and
servers without the possibility of drift. Reduce the amount of `sed`
mangling of the configuration file, and make recommended changes from
`shellcheck` for this section of the provisioning script.

Fixes some rebase errors on the Nomad config as well.

Share base configuration for telemetry and consul. Have the server
configurations respect the `var.server_count` config. Make changes
recommended by `shellcheck` in the provisioning scripts for this section.

Switch to OS/arch-tagged release bundles on S3 for compatibility with
adding Windows builds in the near future.

Match the configuration directory layout we're using for Consul and
other services. Make recommended changes from `shellcheck` for this
section of the provisioning script.

separate vars and outputs into their own files and update default link in nomad binary variable to 0.10.0 release (#6550)

Update the Consul and Vault configs to take advantage of their
included `go-sockaddr` library for getting the IP addresses we need in
a portable way. This particularly avoids problems with "predictable"
interface names provided by systemd.

Also adds the `sockaddr` binary to the Packer build so we can use it
in our provisioning scripts.

docs: Docker driver supports task user option

Make a clear split between Packer and Terraform provisioning steps:
the scripts in the `packer/linux` directory are run when we build the
AMI whereas the stuff in shared are run at Terraform provisioning time.

Merging all runtime provisioning scripts into a single script for each
of server/client solves the following:

* Userdata scripts can't take arguments, they can only be templated
  and that means we have to do TF escaping in bash/powershell scripts.
* TF provisioning scripts race with userdata scripts.

Also, add a test case.

* add nginx to load balancing nav menu and fix bullets

* fill out nginx lb guide

* formatting

* change Nginx to NGINX

* add step to verify load balancer config

* update docker image and web app output

* add HAProxy lb guide

* format haproxy config

* add haproxy stats page with screenshot

* add note about external load balancer

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* add port mapping an static port for haproxy ui + bullet changes

* remove extra spaces

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* Update website/source/guides/load-balancing/haproxy.html.md
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

* add nginx to load balancing nav menu and fix bullets

* fill out nginx lb guide

* formatting

* change Nginx to NGINX

* add step to verify load balancer config

* update docker image and web app output

* change Nginx to NGINX in main load balancing page

* modify change signal to SIGHUP and add else condition in template stanza to prevent nginx from crashing when no services are available to load balance

* add note about external load balancer

* clarifications and link to reference architecture

As the angle bracket invocation RFC says:

> There is no dedicated syntax for passing an "else" block
> directly. If needed, that can be passed using the named
> blocks syntax.

https://github.com/emberjs/rfcs/blob/master/text/0311-angle-bracket-invocation.md#block

Unfortunately, using a contextual component doesn’t help as
the yield inside that component will still result in content
rendering that would show when the source isn’t empty. So
we decided to change the interface so you have to check
whether the source is empty before using it, which aligns with
how list-table works.

docs: job volume spec tasks source, not config > source

docs: fix links to connect

driver/docker: ensure that defaults are populated for dangling containers config

Added version requirement to new feature guides

docs: Added alert to mainpage for new 0.10

Merge 0.10.0 release branch back into master

docs: remove link to 0.10.0-rc1

Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>

docs: bump to Nomad 0.10.0