Resolve TODOs from #2157

[crockeea]

It's unclear if this actually resolves #2157. The TODOs from that issue are no longer relevant, and have been removed. But that issue also mentions

• getting the key switching key added to the IR at a higher level
• getting parameter-selected params forwarded to this lowering

neither of which are done.

[j2kun]

It appears there is a related test failure. Also happy to chat live or email about the next steps

[crockeea]

The test failure is related to a test which was previously disabled, and which, with this PR, became enabled. The test looked very old (it used polynomial.key_switch_inner, an op which I'm not sure ever existed). The appropriate place for this test is in CKKS/Transforms, and that test already exists. As a result, I deleted this test. Should be ready to merge after CI.