Add a Scala/Java version agnostic option for setting the SemanticDB target root and source root directories

[Gedochao]

Fixes #2646

This adds --semanticdb-targetroot and --semanticdb-sourceroot options.
--semanticdb-targetroot accepts a path to the directory, where SemanticDB files should be written.
--semanticdb-sourceroot accepts a path to the directory, from which the relative paths for SemanticDB files should be calculated.

Technically this could have already been done by passing the correct compiler options, but those were very much dependent on a number of things, including Scala/Java version and the manner the semanticdb plugin is passed to the compiler.
The options added here provide unified syntax for all of these cases.

When the target directory is not set, the default follows compiler defaults, which means the semanticdb files are saved alongside compiled class files.

When the source directory is not set, the default follows the Scala CLI project root.
Please note that the Scala CLI project root is not necessarily a parent directory for all project sources.

[tgodzik]

Thanks! LGTM