[WIP] Fix issue with serialization in running multiple modules in parallel.

[nimakarimipour]

This PR fixes #626 which explains how current implementation by using a fixed files name for outputs, limits parallelization techniques in environments where multiple execution units are available.

To address this issue, this PR enables NullAway to choose a UUID at the time of initialization, and will use that unique id as a prefix for all serialized outputs. This way, any instance of NullAway will work on a separate set of files and will not encounter any race issues.

File name changes:

• errors.tsv -> UUID-errors.tsv
• fixes.tsv -> UUID-fixes.tsv
• field_init.tsv -> UUID-field_init.tsv

[nimakarimipour]

@lazaroclapp let's not review this PR yet, as I may have found a better solution for this which does not require this change in NullAway.

[msridhar]

@nimakarimipour can we close this one?

[nimakarimipour]

@msridhar Sure, our recent experiments shows the other approach works and this PR is not needed.