chore(typing): Resolve or ignore `pyright`-only warnings

[dangotbanned]

Follow-up to #3585

Overview

• Removes most of the directory/file-level ignores
• Fixes some simpler warnings
• Adds explicit ignore comments on remaining issues

See individual commit messages for additional context:

• (https://github.com/vega/altair/pull/3676/commits/8ff345695780a7a47c5ef60253186dd5ed6e665d)
• (https://github.com/vega/altair/pull/3676/commits/2ab9dbf75624e66277e89130f39a546a077471d1)
• (https://github.com/vega/altair/pull/3676/commits/ea2e446d0795a7198ea10b7aa342e88f8b7888d2)
• (https://github.com/vega/altair/pull/3676/commits/35cabf0a4765584d17144921091957196a93672a)
• (https://github.com/vega/altair/pull/3676/commits/d8dcbd899eec6e2df0d1edf59056d49eae8270db)

No user-facing changes