[BOLT] Report flow conservation scores (#127954)
Add two additional profile quality stats for CG (call graph) and CFG
(control flow graph) flow conservations besides the CFG discontinuity
stats introduced in #109683. The two new stats quantify how different
"in-flow" is from "out-flow" in the following cases where they should be
equal. The smaller the reported stats, the better the flow conservations
are.
CG flow conservation: for each function that is not a program entry, the
number of times the function is called according to CG ("in-flow")
should be equal to the number of times the transition from an entry
basic block of the function to another basic block within the function
is recorded ("out-flow").
CFG flow conservation: for each basic block that is not a function entry
or exit, the number of times the transition into this basic block from
another basic block within the function is recorded ("in-flow") should
be equal to the number of times the transition from this basic block to
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