cmake: get rid of INSTALL_* options and always install all source

Update CONTAINER_REG variable to allow docker images push from forks

cmake: don't use GREATER_EQUAL commands

It seems redundant to keep these options and it complicates
which files are required by which containers. Installing all source
files should not cause any issue as long as they won't be used.

fixes: #955

Merge stable 1.11 into master

Move inline_string and basic_string template helpers out

cleanups in CMake files

cmake 3.3 (which we're using) doesn't support such functions

and cleanup other, locally set variables after use.

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.

of a template_helpers.hpp. The template_helpers.hpp file should
not have any dependencies on libpmemobj-cpp headers.

string_view: change test behavior according to C++ version

string_view: add modifiers API and related libcxx tests

Fix radix_tree::try_emplace

- 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

It will allow pushing docker images on own forks.

- 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