feat: Add longtr support

[gymreklab]

This PR adds explicit support for LongTR VCF files, meaning most commands will now accept --vcftype longtr. Because LongTR is an extension of HipSTR for long reads, the format is very similar to HipSTR and some HipSTR functions are reused. The main difference is the stutter fields are not present.

In fact, in most cases giving a LongTR VCF but specifying --vcftype hipstr should still work fine.

Checklist

• [x ] I've checked to ensure there aren't already other open pull requests for the same update/change
• [ x] I've prefixed the title of my PR according to the conventional commits specification. If your PR fixes a bug, please prefix the PR with fix: . Otherwise, if it introduces a new feature, please prefix it with feat: . If it introduces a breaking change, please add an exclamation before the colon, like feat!: . If the scope of the PR changes because of a revision to it, please update the PR title, since the title will be used in our CHANGELOG.
• [x ] At the top of the PR, I've listed any open issues that this PR will resolve. For example, "resolves #0" if this PR resolves issue #0

• [x ] I've explained my changes in a manner that will make it possible for both users and maintainers of TRTools to understand them

• [x ] I've added tests for any new functionality. Or, if this PR fixes a bug, I've added test(s) that replicate it
• [x ] All directories with large test files are listed in the "exclude" section of our pyproject.toml so that they do not appear in our PyPI distribution. All new files are also smaller than 0.5 MB.
• [ x] I've updated the relevant REAMDEs with any new usage information and checked that the newly built documentation is formatted properly
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[github-actions]

⚠️ Possible file(s) that should be tracked in LFS detected ⚠️

    The following file(s) exceeds the file size limit: 500000 bytes, as set in the .yml configuration files:

    trtools/testsupport/sample_vcfs/associaTR/many_samples_biallelic_dosages.vcf.gz

    Consider using git-lfs to manage large files.

[heliziii]

Hi Melissa, I went through your changes and all is good. Thank you.