modules: prepare local modules list

[dmyger]

Each entry of module list is treated as a directory with a collection of modules. Each module is located in its own separate subdirectory, one level down. Any duplicates of modules with the same name must be removed, and the original order of module declaration must be preserved (so the first module declaration is used, duplicates are ignored).

All directories of the first level within the specified directory of modules should be scanned, and within each of them a search for either the main executable file or the manifest.yaml file is performed. If one of them is found, the name of the directory will be the potential name of the command executed in tt.

The result is a filtered list of directories where found files meet the first requirement of a module.

Blocked with #1012 and #1013 - expecting the list of modules directories is pre-prepared for work.

[oleg-jukovec]

Part of #1015