bcachefs: Inline more of bch2_trans_commit hot path

bcachefs: Inline more of bch2_trans_commit hot path

The main optimization here is that if we let
bch2_replicas_delta_list_apply() fail, we can completely skip calling
bch2_bkey_replicas_marked_locked().

And assorted other small optimizations.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>