Also have zizmor check for low-severity security issues

[AlexWaygood]

Summary

This PR changes our zizmor configuration to also flag low-severity security issues in our GitHub Actions workflows. It's a followup to #14844. The issues being fixed here were all flagged by zizmor's template-injection rule:

Detects potential sources of code injection via template expansion.

GitHub Actions allows workflows to define template expansions, which occur within special ${{ ... }} delimiters. These expansions happen before workflow and job execution, meaning the expansion of a given expression appears verbatim in whatever context it was performed in.

Template expansions aren't syntax-aware, meaning that they can result in unintended shell injection vectors. This is especially true when they're used with attacker-controllable expression contexts, such as github.event.issue.title (which the attacker can fully control by supplying a new issue title).

[...]

To fully remediate the vulnerability, you should not use ${{ env.VARNAME }}, since that is still a template expansion. Instead, you should use ${VARNAME} to ensure that the shell itself performs the variable expansion.

Test Plan

I tested that this passes all zizmore warnings by running pre-commit run -a zizmor locally. The other test is obviously to check that the workflows all still run correctly in CI 😄

[dhruvmanila]

Looks good