fix(new-execution): always inline execute_impl

[shuklaayush]

• use #[inline(always)] to be consistent
• no significant perf difference (benchmark)

[github-actions]

group	app.proof_time_ms	app.cycles	app.cells_used	leaf.proof_time_ms	leaf.cycles	leaf.cells_used
verify_fibair	(-13 [-1.2%]) 1,078	322,700	17,672,408	-	-	-
fibonacci	(-15 [-0.7%]) 2,122	3,000,420	51,503,521	-	-	-
regex	(+18 [+0.3%]) 6,988	8,217,194	163,669,874	-	-	-
ecrecover	(-14 [-1.2%]) 1,123	274,568	8,596,011	-	-	-
pairing	(-12 [-0.3%]) 3,642	3,725,930	93,105,105	-	-	-

Commit: 387371f

Benchmark Workflow

[codspeed-hq]

CodSpeed WallTime Performance Report

Merging #1919 will improve performances by 44%

_{Comparing fix/new-exec-inline-execute-impl (387371f) with feat/new-execution (4a02a39)}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

⚡ 2 improvements
✅ 22 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	benchmark_execute[bubblesort]	41.6 ms	34.3 ms	+21.48%
⚡	benchmark_execute[quicksort]	55.5 ms	38.5 ms	+44%