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

string_view: add relational operators for string_view class

- add -Ob3 flag to avoid C1064 error in Windows environment

- extend tests to test also wchar_t type

- port libcxx tests to use pmem::obj::string_view class

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

- add missing relational operators for string_view

Fix comparison between n->byte and key.size(). When using pmem::obj::string
or inline_string the behavior was ok (since we always have null terminator
at the end), but we technically access out-of-range memory which can cause
asserts in string_view operator[].

examples: update min cmake version to 3.4

fix default bytes_view in radix_tree

radix_tree improvements