SHARC-212 Update rubocop exclude inheritance

[mkrumholz]

The inherit_mode merge type "Exclude" allows this repo to inherit the excluded files list from panolint-ruby since this config inherits from that .rubocop.yml file. This is necessary because files that aren't required for rubocop to pass locally (e.g. the vendor files specified here) can fail to pass rubocop when tests run in the CI pipeline. We want to ensure that repos using this gem have consistent sets of files excluded, though more can be added to the defaults. In NDS, we also merge in additional exclusions here.

Testing:

• Tested with the metrics-recorder repo, which is still currently using the old panolint gem. To test, I updated the repo to install this gem from this specific branch, as well as panolint-ruby (from the "main" branch). I bundle installed, ran local tests for the repo, ran rubocop locally, then also pushed a build to CI to ensure it passed (it did pass, which it did not when using the "main" branch of the panolint-rails gem without merging the exclude list in metrics-recorder's rubocop.yml file).
• Tested with nds, which is the only repo currently using this gem. I updated NDS to pull from this branch and bundle installed overcommit gems. Confirmed it pulled using this branch and then I ran rubocop. The same violations appeared there as with the "main" branch.

[amymliebs]

Looks great, thank you for the thorough description and testing notes!