[experiment] more tracing span to identify mpcs latency breakdown on flamegraph

[hero78119]

This PR just add tracing span to measure the mpcs break down and visualized in flamegraph

Also attachmented framegraph (its svg file and please download it local then open in browser which allow iteractive navigating)

The bottleneck part probably not on sumcheck, and instead it's from compute_inner_ext and root_from_inner operation

ceno/mpcs/src/basefold/commit_phase.rs

Lines 458 to 461 in a756f46

	running_tree_inner = MerkleTree::<E>::compute_inner_ext(&new_running_oracle);
	let running_root = MerkleTree::<E>::root_from_inner(&running_tree_inner);
	write_digest_to_transcript(&running_root, transcript);
	exit_span!(inner_span);

[hero78119]

related to #568

[hero78119]

More added on: the latency breakdown

• 75% time on mpcs
• 25% time on opcode/table sumckeck proof

So optimize mpcs at current stage will be more huge gain.

In another follow up #537 (comment) the improvement only <15% overall is because it only affect opcode proof sumcheck part. mpcs got another sumcheck implementation and we plan to merge it in issue #558

In overall, as mpcs occupied more time (til 7 Nov '24), any improvement on mpcs will have better impact on overall throuput.