heterogenerous methods for radix_tree

inline_string: API extension

- modify existing inline_string to check new API

- add two string methods

run coverage job on GHA

cleanup in docker scripts after latest doc job changes

Add conversion operator to basic_string

inline_string reimplementation

Add case to cover conversion operator

Implement conversion operator from string to string_view

- change implementation to template
- move functions definitions outside class

remove doubled clang-format configuration's rule

minor comments updates

- update comments,
- update RELEASE_STEPS.md,
- remove unused code and variables.

and remove coverity job from GHA, it will be run as separate workflow.

Add new cases to fully cover inline_string

fix issues from klocwork and coverity

tests: add libunwind suppresion

Radix tree optimizations

Run docs update as separate job on GHA

Memcheck reports an error in libunwind exception raising.

The only difference between lower and upper bound is behavior in
case the element already exists.

to increase lower_bound coverage.

to helper methods.

Change bottom_leaf to return any leaf placed lower than a certain depth.
This way, leaf variable in internal_emplace will always point to an
element with specified key (if only it exists). It saves going descending
the tree for the second time when the element is an embedded entry.

Implementation of basic_string_view class