and use it in jobs not requiring image rebuilding.

instead of using array of hard-coded dir names.

fixes warning in log: 'Unable to find image '...' locally'.

so we don't have to update this piece of code every release.

and let other OSes build independently.

to make possible to override it for testing on real pmem. Default: ON.

to avoid warnings in build logs.

in run-doc-update.sh created PRs.

and additional minor cleanups in run-doc-update.sh

and don't build docs.

- tidy up workflow files,
- make scripts more verbose,
- unify printed messages,
- use proper ${} bash variables syntax,
- order code,
- remove redundant code.

Merge stable-1.11 into master

modify slice to work with output iterators

radix_tree: fix use after free

Iterator inside erase() cannot be incremented after calling delete_persistent.
Incrementing checks the value of leaf_->parent which means reading from free'd memory.

Merge stable-1.10 into stable-1.11

basic_string: remove workaround to compile under VC++2015

After added conversion operators there is no need
to manually cast string to string_view. Casting in this case
produces VC++2015 errors due to operator==() ambiguity.

Merge stable-1.9 into stable-1.10

docker: add Ubuntu-18.04 docker image and test it in other_OSes.yml

CI: use special environment var in GHA for Windows' PATH

The old 'addPath' is depreciated now. For more details see:
https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

Fix TBB cmake

string_view: VS2015 build fix

- remove class namespaces before class members which
  are in the same namespace to avoid compilation errors

- print more concise messages,
- make it required when TESTS_TBB is on.

string: unify description of find API

- change description to be the same for string and string_view

string_view: move find API implementation from string

- change function body to use conversion operator to string_view and
  call find*/rfind* function accordingly

- add find*, rfind* functions to string_view

Bump OSes versions