Add a method on Template to fixmate information

[nh13]

Add a method fixmate on Template that will set mate flags and appropriate SAM tags. This is useful when we modify the records (e.g. clipping) in a template and want to update the tags.

For a code example, see fgbio's fixMateInfo and how it uses htsjdk's setMateInformationOnSupplementalAlignment. Note: we already have a method set_pair_info in fgpyo that will reset mate info for primary records in a pair where both records are mapped.

One can also validate this by running both/either fgbio SetMateInformation or samtools fixmate. Probably a good idea to do both.

Tests should include templates with:

• only primary records
• one or both ends unmapped
• secondary records (are not updated)
• supplementary records (are updated)

Ideally the fixmate method on Template routes to set_pair_info and creates a new method set_pair_info_on_supplementary, as these methods are useful in their own right.