Grouped update with one commit per dependency in a single PR

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

The functionality for grouped updates is very nice! Would it be possible to, instead of creating a single PR consisting of a single commit updating all the dependencies, create a single PR consisting of one commit per updated dependency?

Then we would have these different configuration options:

**No grouping** (possible today)
- PR: `Bump friendsofphp/php-cs-fixer from 3.34.1 to 3.37.0`
- Commit: `Bump friendsofphp/php-cs-fixer from 3.34.1 to 3.37.0`
- PR: `Bump phpstan/phpstan from 1.10.38 to 1.10.39`
- Commit: `Bump phpstan/phpstan from 1.10.38 to 1.10.39`

**Grouping with single commit** (possible today)
- PR: `Bump the dev-dependencies group with 2 updates`
- Commit: `Bump the dev-dependencies group with 2 updates`

**Grouping with individual commits** (the requested feature)
- PR: `Bump the dev-dependencies group with 2 updates`
- Commit: `Bump friendsofphp/php-cs-fixer from 3.34.1 to 3.37.0`
- Commit: `Bump phpstan/phpstan from 1.10.38 to 1.10.39`

I think this would give the best of both worlds:
- Fewer PRs (less noise, fewer rebases, lower build cost)
- Explicit commit messages, showing the dependency name and version
- More granular history, allowing to find the exact dependency that introduced an issue using tools like `git bisect`

For dependencies that must be updated together, they must of course be combined in a commit, just as they are without grouping.

Use the requested behavior as the specification and trace how grouped updates create a pull request and its commits. Confirm how dependencies that must update together are identified. Done means one grouped PR contains separate commits for independent dependencies while coupled dependencies remain in a shared commit.

Written by the indexing model from the issue text.