[NFC] Eliminate use of `lookupLLVMIntrinsicByName` in Coroutines (#114851)
Eliminate use of `lookupLLVMIntrinsicByName` from Coroutines in
preparation of changing it to support a different form of intrinsic name
table generated by intrinsic emitter.
Also eliminate call to `isCoroutineIntrinsicName` from
`declaresAnyIntrinsic` as the list of names traversed is the same list
which `isCoroutineIntrinsicName` checks.