fix: add std feature to openvm-prof serde

[stephenh-axiom-xyz]

No description provided.

[github-actions]

group	app.proof_time_ms	app.cycles	app.cells_used	leaf.proof_time_ms	leaf.cycles	leaf.cells_used
verify_fibair	(+11 [+4.2%]) 274	322,610	2,058,654	-	-	-
fibonacci	(+7 [+0.7%]) 941	1,500,210	1,060,232	-	-	-
regex	(-66 [-2.5%]) 2,625	4,108,483	13,403,604	-	-	-
ecrecover	(-11 [-1.3%]) 864	140,497	2,275,056	-	-	-
pairing	(+6 [+0.4%]) 1,451	1,882,939	23,722,622	-	-	-

Commit: a96af77

Benchmark Workflow