Prepare for v0.37 release

[pjbgf]

The 0.37 release comes with soft decommissioning of libgit2.

TODOs:

• Release go-git with latest changes
• gogit: Add new ForceGoGitImplementation FeatureGate source-controller#945
• gogit: Add new ForceGoGitImplementation FeatureGate image-automation-controller#452
• Remove file reading from bootstrap package #3249
• Refactor Git operations and introduce go-git support for Azure DevOps and AWS CodeCommit #3273
• Bump pkg's dependencies
• Bump pkg/git/*
• Update flux bootstrap git documentation
  • AWS Code Commit
  • Azure DevOps
• Include Aggregate errors in uninstall functions #3294

Release checklist:

• source-controller v0.32.1
• image-automation-controller v0.27.0
• notification-controller v0.29.0
• flux2 v0.37.0
• terraform-provider-flux v0.21.0
• kustomize-controller v0.31.0
• helm-controller v0.27.0
• image-reflector-controller v0.23.0

Documentation updates:

• Add information about new feature flags for source-controller
• Add information about new feature flags for image-automation-controller
• Publish Flux release change log to GitHub & Slack