[DOC] Fix page weights for the table of contents

[knylander-grafana]

This doc PR does several things:

• Fixes a few minor linting issues
• Corrects the page weight for the table of contents
• Updates some text to use Alloy and Agent
• Added the Alloy admonition to one of the pages

[github-actions]

This PR must be merged before a backport PR will be created.

[simonswine]

LGTM

[github-actions]

The backport to release/v1.5 failed:

Validation Failed: "Could not resolve to a node with the global id of 'T_kwDOAG3Mbc4AczmP'."

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-3301-to-release/v1.5 origin/release/v1.5
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x eb9dd3c9604cf8706f334841312d43cc0bc9d427

When the conflicts are resolved, stage and commit the changes:

git add . && git cherry-pick --continue

If you have the GitHub CLI installed:

# Push the branch to GitHub:
git push --set-upstream origin backport-3301-to-release/v1.5
# Create the PR body template
PR_BODY=$(gh pr view 3301 --json body --template 'Backport eb9dd3c9604cf8706f334841312d43cc0bc9d427 from #3301{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title "[release/v1.5] [DOC] Fix page weights for the table of contents" --body-file - --label "type/docs" --label "backport" --base release/v1.5 --milestone release/v1.5 --web

Or, if you don't have the GitHub CLI installed (we recommend you install it!):

# Push the branch to GitHub:
git push --set-upstream origin backport-3301-to-release/v1.5

# Create a pull request where the `base` branch is `release/v1.5` and the `compare`/`head` branch is `backport-3301-to-release/v1.5`.

# Remove the local backport branch
git switch main
git branch -D backport-3301-to-release/v1.5