feat: Add validation to _from_gnomad in translator

[korikuzma]

Close #147

• Update regex for input str
  • Based off of the The Variant Call Format Specification that @wesleygoar sent me:
  
• Validate that expected reference sequence matches actual reference sequence
• Cassettes were automatically generated
• Updated translator test to match latest VRS docs example since the previous test had an invalid reference sequence

[korikuzma]

See this comment regarding requiring valid input or not: #147 (comment)

[korikuzma]

I decided to raise a ValueError if require_validation=True since these lines in translate_from would not give a descriptive error message

vrs-python/src/ga4gh/vrs/extras/translator.py

Lines 81 to 82 in 7cd0c83

	if o is None:
	raise ValueError(f"Unable to parse data as {fmt} variation")

Open to other ways of implementing!