perf: remove `ExecutionCtx` from `OperationsVTable::scalar_at` #7417

Performance Regression: -22.79%

⚡ 4 improved benchmarks
❌ 2 regressed benchmarks
✅ 1117 untouched benchmarks
⏩ 1455 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Simulation	`case_when_all_false[1000]`	85 µs	108.1 µs	-21.37%
⚡	Simulation	`case_when_fragmented[100]`	155.1 µs	133.3 µs	+16.33%
⚡	Simulation	`scalar_at_struct_simple`	594.8 µs	526.6 µs	+12.96%
⚡	Simulation	`scalar_at_struct_wide`	2.7 ms	2.4 ms	+14.31%
⚡	Simulation	`patched_take_10k_first_chunk_only`	329.9 µs	271.1 µs	+21.69%
❌	Simulation	`null_count_run_end[(10000, 4, 0.01)]`	104.2 µs	135 µs	-22.79%

_{Comparing ad/remove-ctx-from-scalar-at (242101f) with develop (71089dd)}

1455 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩