feat!: use materialized view for tx-exon alignment lookup

[jsstevenson]

close #461

• Use the equivalent materialized view for this lookup. It's a small speedup but it only took a few minutes to fix (I think the view just exists as a referent for building the materialized view)
• Rename methods regarding "tx_exon_aln_v" to just "tx_exon_aln", since the Python user doesn't really care that it's a view or a materialized view or whatever, they just need the "tx-exon aln" part. Hopefully this isn't too annoying to change wherever else it's used but if it is, this part could be walked back