Revise initialization and processing test configs

[nulls]

As described in #404 (a fix for #403), save-cli has two steps: discovering and processing test configs (save.toml). Currently, we save-cli expects a first argument for working dir, but we search save.toml in parents, but processes only test configs from provided folder.

We can revise it and load always all tests and use the first argument as only filter for test suites

[petertrr]

Does current logic also affect placing of resources required by execCmd? I.e., if we place executables in the top level folder and try to run tests with subfolder as root, will execution fail on missing files?

[nulls]

if we place executables in the top level folder and try to run tests with subfolder as root, will execution fail on missing files? It doesn't, after fixing processing parent config (#404) -- it does work

Found: we run exeCmd using testConfig.getRootConfig().directory.toString() as a working dir