This changeset is part of the work to improve our E2E provisioning
process to allow our upgrade tests:

* Move more of the setup into the AMI image creation so it's a little
 more obvious to provisioning config authors which bits are essential
 to deploying a specific version of Nomad.

* Make the service file update do a systemd daemon-reload so that we
  can update an already-running cluster with the same script we use to
  deploy it initially.

cli: add system command and subcmds to interact with system API.

The system command includes gc and reconcile-summaries subcommands
which covers all currently available system API calls. The help
information is largely pulled from the current Nomad website API
documentation.

Remote agent pprof endpoints

connect: configure envoy to support multiple sidecars in the same alloc

comment why we ignore errors parsing params

Address pr feedback, rename profile package to pprof to more accurately
describe its purpose. Adds gc param for heap lookup profiles.

fix test expectation

test wrapNonJSON

Passes in agent enable_debug config to nomad server and client configs.
This allows for rpc endpoints to have more granular control if they
should be enabled or not in combination with ACLs.

enable debug on client test

prevent region forwarding loop, backfill tests

fix failing test

helper func to return serverPart based off of serverID

tidy up, add comments

clean up seconds param assignment

m -> a receiver name

return codederrors, fix query

rename implementation method

Return rpc errors for profile requests, set up remote forwarding to
target leader or server id for profile requests.

server forwarding, endpoint tests

wip, agent endpoint and client endpoint for pprof profiles

agent endpoint test

When multiple Connect-enabled task groups start on the same client
node, a race condition in the CNI plugins for creating iptables chains
causes one of the tasks to fail. We upstreamed a patch to CNI plugins
to make iptables chain creation idempotent.

This changeset updates end-to-end testing, development tooling, and
documentation to use 0.8.4 which includes our patch.

In 0.10.2 (specifically 387b016a) we added interpolation to group
service blocks and centralized the logic for task environment
interpolation. This wasn't also added to script checks, which caused a
regression where the IDs for script checks for services w/
interpolated fields (ex. the service name) didn't match the service ID
that was registered with Consul.

This changeset calls the same taskenv interpolation logic during
`script_check` configuration, and adds tests to reduce the risk of
future regressions by comparing the IDs of service hook and the check hook.

[docs] Change consul agent note to callout