Docs: Rename variables pages

[imatwawana]

This PR:

• Updates menuTitle and page title of the Manage variables page to Add variables
• Updates the title of Inspect variables page to Manage and inspect variables (menuTitle remains as is)
• Moves the paragraph of “manage” content from the new Add variables page to the new Manage and inspect variables page

Justification

• This keeps everything that’s in the configuration UI on one page and everything on the Variables page UI on another page
• The original file name of the Manage variables page is add-tempate-variables and the content is primarily about adding them and all the different types that you can add
• When I was on the Inspect variables (docs) page and realized it was about actions you could take on the main Variables page in the UI, I expected to find the rest of the actions I could take on this page here

[grafana-delivery-bot]

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

[grafana-delivery-bot]

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

[grafana-delivery-bot]

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

[grafana-delivery-bot]

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

[grafana-delivery-bot]

The backport to v10.3.x 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-87844-to-v10.3.x origin/v10.3.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 197ce3042d6760530a32819a924ddbf09bf0af2c

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-87844-to-v10.3.x
# Create the PR body template
PR_BODY=$(gh pr view 87844 --json body --template 'Backport 197ce3042d6760530a32819a924ddbf09bf0af2c from #87844{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title '[v10.3.x] Docs: Rename variables pages' --body-file - --label 'type/docs' --label 'no-changelog' --label 'backport' --base v10.3.x --milestone 10.3.x --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-87844-to-v10.3.x

# Create a pull request where the `base` branch is `v10.3.x` and the `compare`/`head` branch is `backport-87844-to-v10.3.x`.

# Remove the local backport branch
git switch main
git branch -D backport-87844-to-v10.3.x

[grafana-delivery-bot]

The backport to v11.0.x 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-87844-to-v11.0.x origin/v11.0.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 197ce3042d6760530a32819a924ddbf09bf0af2c

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-87844-to-v11.0.x
# Create the PR body template
PR_BODY=$(gh pr view 87844 --json body --template 'Backport 197ce3042d6760530a32819a924ddbf09bf0af2c from #87844{{ "\n\n---\n\n" }}{{ index . "body" }}')
# Create the PR on GitHub
echo "${PR_BODY}" | gh pr create --title '[v11.0.x] Docs: Rename variables pages' --body-file - --label 'type/docs' --label 'no-changelog' --label 'backport' --base v11.0.x --milestone 11.0.x --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-87844-to-v11.0.x

# Create a pull request where the `base` branch is `v11.0.x` and the `compare`/`head` branch is `backport-87844-to-v11.0.x`.

# Remove the local backport branch
git switch main
git branch -D backport-87844-to-v11.0.x