Final manual curation in preparation for global `clang-format`ing (#3712)

* Manual line breaks to pre-empt undesired `clang-format`ing.

Informed by work under https://github.com/pybind/pybind11/pull/3683:

https://github.com/pybind/pybind11/commit/60b7eb410fefe2b23aeb6906f2a9184e91b11a15

https://github.com/pybind/pybind11/commit/59572e65598b4b9f2c9ae0b8a0e5fcb6d65c7f92

* Manual curation of clang-format diffs involving source code comments.

Very labor-intensive and dull.

* Pulling .clang-format change from @henryiii's https://github.com/pybind/pybind11/pull/3683/commits/9057962d40ca520b9d26abbe0ff125796e2323dd



* Adding commonly used .clang-format `CommentPragmas:`

* Ensure short lambdas are allowed

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>