added ref and chosen haplotype len to ImputationMetrics

[lynnjo]

Description

Added columns RefLen and HaplotypeLen to the ImputationMetrics output

Type of change

What type of changes does your code introduce? Put an x in boxes that apply.

• [ ] CHANGE (fix or feature that would cause existing functionality to not work as expected)
• [ ] FEATURE (non-breaking change which adds functionality)
• [ ] BUGFIX (non-breaking change which fixes an issue)
• [x] ENHANCEMENT (non-breaking change which improves existing functionality)
• [ ] NONE (if none of the other choices apply. Example, tooling, build system, CI, docs, etc.)

Checklist:

• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have updated relevant documentation

Changelog entry

Please add a one-line changelog entry below. This will be copied to the changelog file during the release process.

Added RefLen and HaplotypeLen columns to ImputationMetrics output

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 81.12%. Comparing base (4827786) to head (bb5eed4). Report is 5 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #242 +/- ## ========================================== + Coverage 81.10% 81.12% +0.02% ========================================== Files 81 81 Lines 5784 5792 +8 Branches 1025 1025 ========================================== + Hits 4691 4699 +8 Misses 718 718 Partials 375 375 ```

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