Make some ifs constexpr

[the-moisrex]

This makes some ifs if constexprs even though it has no affect in the benchmarks, but it's better to be explicit.

Also removed a useless enum.

[the-moisrex]

Also, I'm getting these warnings:

/ada-url/benchmarks/benchmark_template.cpp:27:9: warning: ‘++’ expression of ‘volatile’-qualified type is deprecated [-Wvolatile]
   27 |         success++;
      |         ^~~~~~~
/ada-url/benchmarks/benchmark_template.cpp:42:11: warning: ‘++’ expression of ‘volatile’-qualified type is deprecated [-Wvolatile]
   42 |           success++;
      |           ^~~~~~~
/ada-url/benchmarks/benchmark_template.cpp: In function ‘void Bench_BasicBench_AdaURL_CanParse(benchmark::State&)’:

[codspeed-hq]

CodSpeed Performance Report

Merging #1037 will improve performances by 17.56%

_{Comparing the-moisrex:benchmark-constexpr (d3867e2) with main (236e519)}

Summary

⚡ 1 improvement
✅ 18 untouched
⏩ 3 skipped¹

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	BasicBench_whatwg	31.7 µs	27 µs	+17.56%

Footnotes

1. 3 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. ↩

[anonrig]

Also, I'm getting these warnings:

/ada-url/benchmarks/benchmark_template.cpp:27:9: warning: ‘++’ expression of ‘volatile’-qualified type is deprecated [-Wvolatile]

   27 |         success++;

      |         ^~~~~~~

/ada-url/benchmarks/benchmark_template.cpp:42:11: warning: ‘++’ expression of ‘volatile’-qualified type is deprecated [-Wvolatile]

   42 |           success++;

      |           ^~~~~~~

/ada-url/benchmarks/benchmark_template.cpp: In function ‘void Bench_BasicBench_AdaURL_CanParse(benchmark::State&)’:

this should be fixed too... no rush