Allow comparison with a commit different from last one

From the beginning, we made sure the program isn't blocked to comparing a file only with its last revision. Our script takes two commit hashes, and this allows reusability for a [1 commit to N commits comparison](https://github.com/chocoteam/PerformanceAction/issues/15). Another idea was to allow a comparison with the last minor/major release, which would be possible.

To make it configurable, we'd like to add a `"compare_with"` option to the GitHub Action which would accept:

- (`last commit`: Compare every changed file with last commit (same result as `last-revision`))
- `last revision` **or nothing**: Compare every changed file with their last revision
- `average of [N] revisions`: Compare every changed file with their N last revisions (making an average of past results)
- `last patch`: Compare every changed file with their version in the last patch release (`X.X.N`)
- `last minor`: Compare every changed file with their version in the last minor release (`X.N.X`)
- `last major`: Compare every changed file with their version in the last major release (`N.X.X`)
- _Anything else_: Treated as a commit hash → Compare every changed file with their version at the given hash

The problem is: there is no relationship between a commit hash in the [choco-solver](https://github.com/chocoteam/choco-solver) repo and this one. Same goes for releases.