Revised NomadProject Structure

remove Index field from EmitNodeEventsResponse

Removed Terraform mention in integrations without existing guide.

copied consts used by jobspec parsing from structs into api package, to avoid referencing structs package in jobspec (#5663)

Consul Catalog Integration Fixes

docs: Change querystring -> query string

- Revised "What is Nomad" copy
- Added "Key Features" section with links to task drivers & device plugins with lift-and-shift from README
- Added "Who Uses Nomad" section with users, talks, blog posts
- Removed Hadoop YARN, Docker Swarm, HTCondor from comparisons
- Revamped Guides section
- Inserted "Installing Nomad", "Upgrading", "Integrations" as persistent in Guides navbar
- Split Installing Nomad into two paths for users (one for Sandbox with "Quickstart", one for Production)
- Surfaced "Upgrading" and "Integrations" section from documentation
- Changed "Job Lifecycle" section into "Deploying & Managing Applications"
- Reworked "Operations" into "Operating Nomad"
- Reworked "Security" into "Securing Nomad"
- Segmented Namespaces, Resource Quotas, Sentinel into "Governance & Policy" subsection
- Reworked "Spark integration" into its own "Analytical Workloads" section

Remove unnecessary locking and serverlist syncing in heartbeats

* Typo fixes
* it's -> its
* plugable -> pluggable

`Index` is already included as part of `WriteMeta` embedding.

This is a backward compatible change: Clients never read the field; and
Server refernces to `EmitNodeEventsResponse.Index` would be using the
value in `WriteMeta`, which is consistent with other response structs.

* client: was not using up-to-date client state in determining which alloc count towards allocated resources

* Update client/client.go
Co-Authored-By: cgbaker <cgbaker@hashicorp.com>

docs: fix default restart values

Fixed Typo

Fixed typo: schedular/scheduler.

E2E Test Terraform/Packer Improvements

Add config to disable preemption for batch/service jobs

Converts ANSI terminal codes to HTML in logs

This removes an unnecessary shared lock between discovery and heartbeating
which was causing heartbeats to be missed upon retries when a single server
fails. Also made a drive by fix to call the periodic server shuffler goroutine.

Codegen codec helpers for all nomad structs

config parse direct hcl

fix system sched constraint errors

docs: update s3 urls to use virtual bucket style

Update peers info with new raft config details

In response to https://forums.aws.amazon.com/ann.jspa?annID=6776

Fix Typo