(deps/types/clean): remove extraneous typings

[agilgur5]

• external @types/ are overridden by the package's own internal
  typings, so any @types/ packages on top of that are extraneous

  • and are usually deprecated too; all are in this case

• execa has had its own typedefs since v2

  • the @types/execa package is very dated at v0.9

• ora has had its own typedefs since v3.2

  • so @types/ora v3.2 is just a stub

• ansi-escapes has had its own typedefs since v4

  • @types/ansi-escapes v4 is just a stub

• camelcase has had its own typedefs since v5.2

  • @types/camelcase v5.2 is just a stub
  • pin camelcase to v5.2+ from 5.0 to ensure it's a version with
    internal typings

• ora also had an unnecessary internal re-declaration too

• as did ansi-escapes and camelcase

---

(docs/types): add comments to some remaining declarations

• clarify why some of these internal declarations/re-declarations
  are necessary
  • I tried removing them because I didn't know why they were needed,
    so this documentation should be helpful

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Hard to say where these made their way in / root cause, seems to have just happened while upgrading / downgrading deps or conversion to TS in #246, #247, #54, and probably some others.

[agilgur5]

LGTM. Remember to rebase this in instead of squash as there's two separate commits (split the docs/comments one out)