Currently, running mtr with an incorrect (for example, new or
obsolete) version of wsrep_provider (for example, with the 26
version of libgalera_smm.so) leads to the failure of tests in
several suites with vague error diagnostics.

As for the galera_3nodes suite, the mtr also does not effectively
check all the prerequisites after merge with MDEV-18426 fixes.
For example, tests that using mariabackup do not check for presence
of ss and socat/nc. This is due to improper handling of relative
paths in mtr scripts.

In addition, some tests in different suites can be run without
setting the environment variables such as MTR_GALERA_TFMT, XBSTREAM,
and so on.

To eliminate all these issues, this patch makes the following changes:

1. Added auxiliary wsrep_mtr_check utility (which located in the
mysql-test/lib/My/SafeProcess subdirectory), which compares the
versions of the wsrep API that used by the server and by the wsrep
provider library, and it does this comparison safely, without
accessing the API if the versions do not match.

2. All checks related to the presence of mariabackup and utilities
that necessary for its operation transferred from the local directories
of different mtr suites (from the suite.pm files) to the main suite.pm
file. This not only reduces the amount of code and eliminates duplication
of identical code fragments, but also avoids problems due to the inability
of mtr to consider relative paths to include files when checking skip
combinations.

3. Setting the values of auxiliary environment variables that
are necessary for Galera, SST scripts and mariabackup (to work
properly) is moved to the main mysql-test-run.pl script, so as
not to duplicate this code in different suites, and to avoid
partial corrections of the same errors for different suites
(while other suites remain uncorrected).

4. Fixed duplication of the have_file_key_management.inc and
have_filekeymanagement.inc files between different suites,
these checks are also transferred to the top level.

5. Added garbd presence check and garbd path variable.

https://jira.mariadb.org/browse/MDEV-18565