Add support for Scribble instrumentation metadata for a Fuzz feature

[blitz-1306]

Changes

• Tweaked ScribbleMixin to use --instrumentation-metadata-file option of Scribble and store metadata at path of SCRIBBLE_ARMING_META_FILE constant (for now it is .scribble-arming.meta.json in the CWD). Arming is generating the metadata file. Disarming will remove it.
• Introduced ScribbleMixin.get_arming_instr_meta() static method for an convenient access to the generated metadata file contents in other classes.
• Tweaked fuzz_run to add (if present) data from ScribbleMixin.get_arming_instr_meta() to the submission payload.

Notes

I guess it would be better to add a CLI option to override output location for a generated metadata. The current value (.scribble-arming.meta.json in constant SCRIBBLE_ARMING_META_FILE) can be used as a default.

Related links

• Scribble instrumentation metadata format description
• Scribble instrumentation metadata generation options via CLI

Regards.