[FR]: Make freeze logic on install more convenient to end users

### What is the current behavior?

Currently, a user must export `ASPECT_RULES_JS_FROZEN_PNPM_LOCK` to enable `update_pnpm_lock` failures on CI for non frozen installs.

### Describe the feature

Instead of having the users of this rule know a magic variable, just check for a common one like `CI` so that this works out of box without confusing the end user. A great package for simplifying this check is https://www.npmjs.com/package/env-ci which will do all the necessary checks for you.

### Fund our work

- [ ] Sponsor our open source work by donating a [feature bounty](https://opencollective.com/aspect-build/)

Start at the update_pnpm_lock rule and inspect how ASPECT_RULES_JS_FROZEN_PNPM_LOCK currently controls failures. Review the proposed env-ci package's CI detection, then verify that non-frozen installs fail under CI without the magic variable while local installs retain their current behavior.

Written by the indexing model from the issue text.