execution/vm: migrate benchmarks to b.Loop()

[Copilot]

Migrates VM benchmarks to use Go 1.24's b.Loop() pattern, replacing the traditional for i := 0; i < b.N iteration.

Changes

• Benchmark iteration: Replaced for i := 0; i < b.N loops with b.Loop() across all VM benchmark tests
• Timer management: Moved b.ResetTimer() calls before loops, removed manual b.StartTimer()/b.StopTimer() pairs where b.Loop() handles timing automatically
• Test files affected: analysis_test.go, evm_test.go, gas_table_test.go, instructions_test.go, memory_test.go, program/program_test.go, runtime/runtime_test.go

Example

Before:

for i := 0; i < b.N; i++ {
    contract := NewContract(addr, addr, addr, value, cache)
    // benchmark code
}

After:

contract := NewContract(addr, addr, addr, value)
b.ResetTimer()
for b.Loop() {
    // benchmark code
}

This change improves benchmark accuracy by eliminating setup overhead from timing measurements and aligns with Go 1.24's recommended benchmark patterns.

Original prompt

open this as a PR against release/3.3

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