Save example function signature in cloud buckets.

[DonggeLiu]

Currently, we only save existing human-written fuzz targets in the cloud bucket as example solutions.
The corresponding example questions (i.e., signature of the function used in the fuzz targets) are parsed from FI report everytime by the user.

This is problematic because:

1. We cannot access them when the FI report was not available, and
2. It reports distracting errors.
3. Time consuming.

Ideally solution:

1. Add a JSON that maps each fuzz target to a list of signatures of the functions used in the fuzz target.
2. Restructure the code to take function signatures from the bucket and only generate them at runtime if not in the bucket.