[SelectionDAG] Add `STRICT_BF16_TO_FP` and `STRICT_FP_TO_BF16` (#80056)

This patch adds the support for `STRICT_BF16_TO_FP` and
`STRICT_FP_TO_BF16`.

GitOrigin-RevId: 8300f30a9234ee46b2b941e8b07cb7d104c846cb
3 files changed