Removing last remnants of pragma block at the top of pybind11.h (#3186)

* Removing last remnants of pragma block at the top of pybind11.h, defaulting CUDA, GCC7, GCC8 to PYBIND11_NOINLINE_DISABLED, with the option to define PYBIND11_NOINLINE_FORCED.

* Unique SOSIZE prefix to make it easier to extract the sosizes from the GitHub logs.

* Commenting out PYBIND11_WERROR block, for noinline testing.

* Undoing accidental change.

* `#define PYBIND11_NOINLINE_FORCED`

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci



* `#define PYBIND11_NOINLINE_DISABLED`

* Going back to default (removing `#define PYBIND11_NOINLINE_DISABLED`).

* `#define PYBIND11_NOINLINE_FORCED`

* Undoing all changes releated to measuring sosizes.

* Rollback of PR #3030 (Working around Centos 8 failure).

* Disabling -Werror for GNU (experiment).

* Commenting out the entire `if(PYBIND11_WERROR)` again (although that is not expected to make a difference, but who knows what I am overlooking).

* Adding `-DCMAKE_BUILD_TYPE=Release`

* Undoing change to tests/CMakeLists.txt (uncommenting `if(PYBIND11_WERROR)` block).

* post `git rebase master -X theirs` fixups.

* Adding measurements to comment for `PYBIND11_NOINLINE_FORCED`.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>