feat(validation): add Name field validation and improve error output

[KristjanESPERANTO]

• Validate that Name field parts start with language code (2 uppercase letters + space)
• Group errors by file with max 10 errors shown per file
• Add summary with files/errors count

Result with the current issue in the bg data:

$ python3 bin/test_all_tables.py 

======================================================================
VALIDATION FAILED
======================================================================


src/bg/holidays/holidays.public.csv: 64 error(s)
  • (line 9): Name part 'Ден на храбростта и Българската армия' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 9): Name part 'Tag der bulgarischen Armee' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 9): Name part 'and the Bulgarian Army’s Day' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 10): Name part 'Tag der slawischen Literatur' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 10): Name part 'and Slavic Script Day' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 11): Name part 'Tag der slawischen Literatur' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 11): Name part 'and Slavic Script Day (Observed)' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 27): Name part 'Ден на храбростта и Българската армия' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 27): Name part 'Tag der bulgarischen Armee' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  • (line 27): Name part 'and the Bulgarian Army’s Day' must start with a language code (two uppercase letters). Hint: If this text contains a comma, use %2C instead.
  ... and 54 more errors

======================================================================
Summary: 1/146 files with errors (64 total errors)
======================================================================

[HolgerJeromin]

Ref #155

[KristjanESPERANTO]

Now that the bg data has been fixed and I have rebased this PR, the tests are green now, as expected 🙂