it's not needed anymore in the main CMake, since the only test that
was using it, does not require it anymore. It's moved to a function
in a helper file for potential future use.

- add more and fix comments,
- group commands,
- cleanup messages,
- simplify code/commands.

string_view: change test behavior according to C++ version

string_view: add modifiers API and related libcxx tests

- check noexcept when testing our implementation of string_view

- enable tests for remove_suffix/prefix and swap methods

- add remove_prefix, remove_suffix and swap for string_view

- taken from: llvm-mirror/libcxx@78d6a77

string_view: implement iterator API for string_view

- add string_view iterators

- taken from: llvm-mirror/libcxx@78d6a77

- add forward iterator API for string_view

CI: require login to container registry only when pushing image

This reverts commit 07e3fa7b.

Packages should be public now, so they don't require login.
Basically GHCR should work just fine like it was in #930 + commit: da7bdf7c.

Fix GH Container Registry log-in

rather than only in push-image.sh script.

string_view: add missing licence for capacity libcxx test

docker: use GH Container Registry instead of Docker Hub

- add missing Intel licence

and refactor docker scripts a bit.

string_view: implement capacity API and port libcxx tests

- change implementation to use pmem::obj::string_view

- taken from: llvm-mirror/libcxx@78d6a77

- add missing empty and max_size methods required by tests

string_view: implement access API and port libcxx tests

- change implementation to use pmem::obj::string_view

- add missing functions: front, back
- extend declarations by constexpr keyword

- taken from: llvm-mirror/libcxx@78d6a77

Merge changes from stable-1.11 to master

add concurrent_hash_map concurrent erase defrag test

ref: #892

cmake: add ccache support

Move Coverity job to GHA

On my not-so-fast NUC it improves build time:

clean build without ccache (and first build with ccache):
real	6m15.062s
user	19m45.633s
sys	1m48.421s

second clean build with ccache:
real	0m48.836s
user	1m48.793s
sys	0m35.407s

It's not needed for CI, as builds are done in containers and do not share
ccache anyway

add range methods to basic_string

radix_tree: fix internal find