Backport of Update HCP bootstrapping to support existing clusters into release/1.15.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #16916 to be assessed for backporting due to the inclusion of the label backport/1.15.

WARNING automatic cherry-pick of commits failed. Commits will require human attention.

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The below text is copied from the body of the original PR.

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Replaces #16788

Description

We want to allow users to link Consul clusters that already exist to
HCP. Existing clusters need care when bootstrapped by HCP, since we do
not want to do things like change ACL/TLS settings for a running
cluster.

The plan is to only send down a management token to existing clusters
and nothing else (at least initially).

This PR adds a few commits to that end:

• Add an HCP management token to server config so that it can be persisted
  through Raft as we do for the initial management token.
• Update the HCP SDK to be able to receive this new management token.
• Update the bootstrapping logic to account for the different types of
  clusters that are going to be supported.

Best reviewed by commit

Testing & Reproduction steps

• Unit tests

PR Checklist

• updated test coverage
• external facing docs updated
• not a security concern

TODO

• Manual testing

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Overview of commits

• 815c9c1 - a5a08cc - 1daf565 - f798be1

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[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR