support for VCF4.5 just like (vcf4.4) . Changed optimistic_vcf_4_4 to optimistic_vcf_4_x

[lindenb]

Description

This PR add a support to vcf4.5 just like vcf4.4. I changed things like optimistic_vcf_4_4 to optimistic_vcf_4_x.
The PR adds a new VCFHeaderVersion 4_5
The PR adds a new VCF header 4.5 for the tests which is just a copy of the 4.4

Things to think about before submitting:

• Make sure your changes compile and new tests pass locally.
• Add new tests or update existing ones:
  • A bug fix should include a test that previously would have failed and passes now.
  • New features should come with new tests that exercise and validate the new functionality.
• Extended the README / documentation, if necessary
• Check your code style.
• Write a clear commit title and message
  • The commit message should describe what changed and is targeted at htsjdk developers
  • Breaking changes should be mentioned in the commit message.