[DOC] Update Set up test app to use agent flow

[knylander-grafana]

What this PR does:

Updates the Set up the test app doc to use Agent Flow and Intro to MLTP as an option.

Which issue(s) this PR fixes:
Fixes #3226

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[joe-elliott]

Couple o thoughts. I didn't test any of the actual config or steps. Trust these are correct.

[knylander-grafana]

Couple o thoughts. I didn't test any of the actual config or steps. Trust these are correct.

Thank you. You caught some of the places where we had changed from distributor to query but didnt' get all of the changes in the text.

I've asked Heds to do a review to verify that things are correct. When we wrote the doc, he used the configs to make sure that they worked.

[github-actions]

The backport to release-v2.3 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-3228-to-release-v2.3 origin/release-v2.3
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x e11ceb9fcd11382f955dae26439d3ee38eafbc61

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-3228-to-release-v2.3
# Create the PR body template
PR_BODY=$(gh pr view 3228 --json body --template 'Backport e11ceb9fcd11382f955dae26439d3ee38eafbc61 from #3228{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title "[release-v2.3] [DOC] Update Set up test app to use agent flow" --body-file - --label "type/docs" --label "backport" --base release-v2.3 --milestone release-v2.3 --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-3228-to-release-v2.3

# Create a pull request where the `base` branch is `release-v2.3` and the `compare`/`head` branch is `backport-3228-to-release-v2.3`.

# Remove the local backport branch
git switch main
git branch -D backport-3228-to-release-v2.3