chore: stark-backend v0.2.1 and replace AnyRap with AirRef

[jonathanpwang]

closes INT-3054

[github-actions]

group	app.proof_time_ms	app.cycles	app.cells_used	leaf.proof_time_ms	leaf.cycles	leaf.cells_used
verify_fibair	(+154 [+6.6%]) 2,486	513,827	19,376,791	-	-	-
fibonacci_program	(-19 [-0.3%]) 6,017	1,500,137	51,487,838	(-179 [-2.2%]) 7,834	1,832,635	70,691,651
regex_program	(+780 [+4.4%]) 18,684	4,190,904	165,010,909	(-50 [-0.3%]) 17,244	3,028,299	142,199,523
fib_e2e	44,241	12,000,137	410,699,582	54,157	11,453,288	437,452,555
ecrecover_program	(+70 [+2.7%]) 2,689	285,401	15,075,033	(-157 [-0.7%]) 22,558	4,164,912	203,551,317

Commit: 2fe942b

Benchmark Workflow