chore: Remove Vec from MemoryRecord interface

[zlangley]

This allows us to change out the implementation (e.g., SmallVec) without affecting the interface

[jonathanpwang]

Good idea!

[jonathanpwang]

Hm keccak test is failing

[github-actions]

group	app.proof_time_ms	app.cycles	app.cells_used	leaf.proof_time_ms	leaf.cycles	leaf.cells_used
verify_fibair	(-28 [-1.3%]) 2,200	513,772	19,376,241	-	-	-
fibonacci_program	(+6 [+0.1%]) 5,285	1,500,095	51,485,080	-	-	-
regex_program	(-156 [-1.0%]) 15,103	(+2225737 [+116.3%]) 4,139,840	(-1623938 [-1.0%]) 163,831,435	-	-	-
ecrecover_program	(+48 [+1.9%]) 2,594	284,567	15,055,723	-	-	-

Commit: 3f76e13

Benchmark Workflow