Convert remaining pack files to Typescript

[renchap]

The first commit converts all the trivial pack files. @types/webpack-env is added to have the types for require.context() and __webpack_public_path__

The second commit is automated and formats the remaining pack files using Prettier, to reduce the diff for the next commit.

The 3rd commit converts the 2 remaining packs (sign_up and two_factor_authentication).

[ClearlyClaire]

This looks fine on principle, however I think it might be easier to review as well as easier for downstreams to handle if the first two commits were dedicated PRs.

[renchap]

Replaced by #30102, #30105 and #30106