Remove obsolete parser UUID directory

[lm-sousa]

Problem

ParallelCodeParser creates a clava_parsing_<UUID> directory for every parser session and passes it to each ClangAstDumper as a base working directory.

This was added in 74de7332b2226196ee0f63f0953b7848f0ca2ee5 in 2018, when parallel clang-dumper processes emitted dumps and several side files relative to their working directories. The side files were removed from clang-dumper in 1938d184252a277b45e2b7b1751faa9696f49336 after their Java readers became obsolete.

The current dumper can write its primary AST output and dependency file to explicit paths. A parser-wide UUID root, baseFolder, and the associated workingFolders tracking no longer provide isolation that is not already available from per-invocation temporary output paths.

Proposed change

• Remove the clava_parsing_<UUID> session directory.
• Remove the baseFolder plumbing between ParallelCodeParser and ClangAstDumper.
• Remove obsolete multi-folder tracking where each dumper instance now owns one invocation directory.
• Give each dumper invocation an OS-created temporary directory for its explicit AST, dependency, and optional debug outputs.
• Keep the numeric dumper -id mechanism. It is independent and still distinguishes IDs across translation units.

Acceptance criteria

• Parallel parsing of multiple source files still uses independent output paths.
• Concurrent parser sessions cannot overwrite one another.
• Normal and debug cleanup remove only directories owned by that invocation.
• No process working-directory dependency remains.
• Existing parser tests pass with the production clang-dumper that contains 1938d184.