synchro: add fuzzer for ParseISO

[uji]

Implement a fuzzer using the Fuzzing feature of the Go standard and run it continuously with CI.
This is particularly useful in finding vulnerabilities, as it allows them to reach edge cases that are often overlooked by humans.

Details

• Implementation of FuzzParseISO
  • This explores whether there are any cases where ParseISO causes a panic.
  • A similar fuzzer has been implemented in chrono, which served as an inspiration.
• Configuration for automatic execution in CI.
  • To provide rapid feedback to developers before merging into the base branch, Fuzzing will also be conducted in the Test workflow.
  • There are other approaches to test more comprehensively at a lower frequency (often referred to as Batch Fuzzing), but given the size of the codebase, this is considered unnecessary at present, as lightweight Fuzzing can achieve sufficient coverage.
  • Set to 300 second because the increase in 'New interesting' slows down and stops growing.

Graph showing the increase in "New interesting" when running for 10 minutes on GItHub Actions.

References

• Go Fuzzing: https://go.dev/doc/security/fuzz/
• OSS-Fuzz docs: https://google.github.io/oss-fuzz/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.86%. Comparing base (2206fae) to head (215ac01).

Additional details and impacted files

@@             Coverage Diff              @@
##              main      #33       +/-   ##
============================================
- Coverage   100.00%   46.86%   -53.14%     
============================================
  Files           15      434      +419     
  Lines         2635     5659     +3024     
============================================
+ Hits          2635     2652       +17     
- Misses           0     3004     +3004     
- Partials         0        3        +3     

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[Code-Hex]

Great! Thank you so much!