🚀 Add new Agent Token controller

[arybolovlev]

Rollback Plan

If a change needs to be reverted, we will publish an updated version of the library.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

No.

Description

This PR introduces a new controller that enables the management of Agent tokens across arbitrary Agent Pools. The controller can either fully manage the tokens for a pool or merge its tokens with any existing ones. In the latter case, the controller will manage only its own tokens, leaving the others unchanged.

This solution allows the operator to run on multiple clusters and sync tokens for the same pool, with each cluster having its own token(s) for agents.

Tests

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Usage Example

apiVersion: app.terraform.io/v1alpha2
kind: AgentToken
metadata:
  name: this
spec:
  organization: kubernetes-operator
  token:
    secretKeyRef:
      name: hcp-terraform-operator
      key: token
  agentPool:
    name: multik
  agentTokens:
  - name: token-a
  - name: token-b
  secretName: this
  deletionPolicy: retain
  managementPolicy: merge

References

Partially addresses issue #585.

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[jrhouston]

Just a some nitpicky comments, going to approve