This commit adds critical_wakeup_*_* counters to indicate which function
units wake up the instructions in RS. Previously we have wait_for_src_*
counters but they cannot represent where the critical operand (the last
waiting operand) comes from.

We need these counters to optimize fast wakeup logic. If some
instructions critically depend on some other instructions, we can think
of how we can optimize the wakeup process.

Furthermore, this commit also adds a specific counter for FMAs that
wakeup other FMAs' third operand. This helps us to decide which strategy
is used for FMA fast issue.