Add deprecation banner to main index files in Agent

[clayton-cornell]

PR Description

Which issue(s) this PR fixes

Notes to the Reviewer

PR Checklist

• CHANGELOG.md updated
• Documentation added
• Tests updated
• Config converters updated

[grafanabot]

The backport to release-v0.36 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-6843-to-release-v0.36 origin/release-v0.36
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 99b2c127cd71a32276b59f225e68776099adb5b3
# Push it to GitHub
git push --set-upstream origin backport-6843-to-release-v0.36
git switch main
# Remove the local backport branch
git branch -D backport-6843-to-release-v0.36

Then, create a pull request where the base branch is release-v0.36 and the compare/head branch is backport-6843-to-release-v0.36.

[grafanabot]

The backport to release-v0.37 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-6843-to-release-v0.37 origin/release-v0.37
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 99b2c127cd71a32276b59f225e68776099adb5b3
# Push it to GitHub
git push --set-upstream origin backport-6843-to-release-v0.37
git switch main
# Remove the local backport branch
git branch -D backport-6843-to-release-v0.37

Then, create a pull request where the base branch is release-v0.37 and the compare/head branch is backport-6843-to-release-v0.37.

[grafanabot]

The backport to release-v0.38 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-6843-to-release-v0.38 origin/release-v0.38
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 99b2c127cd71a32276b59f225e68776099adb5b3
# Push it to GitHub
git push --set-upstream origin backport-6843-to-release-v0.38
git switch main
# Remove the local backport branch
git branch -D backport-6843-to-release-v0.38

Then, create a pull request where the base branch is release-v0.38 and the compare/head branch is backport-6843-to-release-v0.38.

[grafanabot]

The backport to release-v0.39 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-6843-to-release-v0.39 origin/release-v0.39
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 99b2c127cd71a32276b59f225e68776099adb5b3
# Push it to GitHub
git push --set-upstream origin backport-6843-to-release-v0.39
git switch main
# Remove the local backport branch
git branch -D backport-6843-to-release-v0.39

Then, create a pull request where the base branch is release-v0.39 and the compare/head branch is backport-6843-to-release-v0.39.