feat(transformers): Add beforeDeclarations transformers

[Danielku15]

Fixes #58880

Relates to #17146 and #41486 (not fully fixes them)

The custom transformers were lacking a beforeDeclarations allowing devs to do a AST transformation before the built-in transformers. If you wanted to use information from erased AST nodes (visibility, initializers, etc.) you were lost. With this change devs can improve their JSDoc comments or use other transformations specific for declarations.

Sorry for the PR without Backlog milestone issue. I still hope this makes it through.

[typescript-bot]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[typescript-bot]

Looks like you're introducing a change to the public API surface area. If this includes breaking changes, please document them on our wiki's API Breaking Changes page.

Also, please make sure @DanielRosenwasser and @RyanCavanaugh are aware of the changes, just as a heads up.

[sandersn]

To help with PR housekeeping, I'd prefer not to have PRs for bugs that aren't accepted yet. Discussion usually brings up new implementation requirements, and the codebase can change underneath the PR.

[typescript-bot]

The TypeScript team hasn't accepted the linked issue #58880. If you can get it accepted, this PR will have a better chance of being reviewed.

[Danielku15]

@sandersn Typically I would fully agree that discussion should happen before PRs are opened and features proposed. I still hope that this would be a low-hanging-fruit topic we can easily pick. IMHO it was an oversight to properly add "beforeDeclarations" when "afterDeclarations" transformers were added (considering normal before/after exists too). I really hope that not the whole functionality as such (pre-existing) is being challenged as part of an extension where 3/4 combinations are enhanced to ship 4/4.

As discussion around such topics often happens across years, and is spread across thousands of issues. It is hard to expect people will become active on a new issue. With this I hope the maintainers dive at least a bit into the issue and PR to reflect on it. Its really not such a big deal with direct added benefit. Also considering there is already a tree of partially related issues with interest.