Include instrument name in output metadata TSV

[etal]

PacBio instruments include their name in the header of the unaligned BAM they produce. For each read group (there may be multiple), denoted by the @RG tag , the PL key has the sequencing platform (e.g. PACBIO) and the PM key has the platform model (e.g. REVIO or SEQUELII).

Without requiring additional user input, these values could be extracted from the input BAM and emitted as an additional column in the output metadata TSV.

Fragile example code:

rg = pysam.AlignmentFile(path, "rb").header["RG"][0]
instrument_name = f"{rg['PL']} {rg['PM']}"