Use UInt8 storage for hot parser enums

[dduan]

Switch Token.Kind and InternalTOMLArray.Kind to UInt8-backed enums. The parser compares these enums in tight loops, and smaller enum storage can improve code generation and reduce data movement without changing semantics.

[github-actions]

Comparing results between 'main' and 'pull_request'

Host 'runnervmkj6or' with 4 'x86_64' processors with 15 GB memory, running:
#18~24.04.1-Ubuntu SMP Sat Jun 28 04:46:03 UTC 2025

TOMLDecoderBenchmarks

Decode toml.io example metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	65	66	66	66	70	83	122	7330
pull_request	64	65	66	66	70	84	124	7338
Δ	-1	-1	0	0	0	1	2	8
Improvement %	2	2	0	0	0	-1	-2	8

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	605	605	605	605	605	605	605	7330
pull_request	604	604	604	604	604	604	604	7338
Δ	-1	-1	-1	-1	-1	-1	-1	8
Improvement %	0	0	0	0	0	0	0	8

Parse toml.io example metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ns) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	5440	5531	5551	5603	5643	6723	24105	10000
pull_request	5540	5671	5711	5751	5823	7635	23814	10000
Δ	100	140	160	148	180	912	-291	0
Improvement %	-2	-3	-3	-3	-3	-14	1	0

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	13	14	14	14	14	14	14	10000
pull_request	13	14	14	14	14	14	14	10000
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

decode canada.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	265	265	267	267	268	268	268	4
pull_request	266	266	267	267	267	267	267	4
Δ	1	1	0	0	-1	-1	-1	0
Improvement %	0	0	0	0	0	0	0	0

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	1674	1674	1674	1674	1674	1674	1674	4
pull_request	1674	1674	1674	1674	1674	1674	1674	4
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

decode twitter.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	8781	8806	8823	8839	8897	9142	9457	113
pull_request	8808	8847	8856	8880	8929	9433	9433	112
Δ	27	41	33	41	32	291	-24	-1
Improvement %	0	0	0	0	0	-3	0	-1

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	68	68	68	68	68	68	68	113
pull_request	68	68	68	68	68	68	68	112
Δ	0	0	0	0	0	0	0	-1
Improvement %	0	0	0	0	0	0	0	-1

parse GitHub events archive metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	154	155	155	161	161	161	161	7
pull_request	153	153	154	154	157	157	157	7
Δ	-1	-2	-1	-7	-4	-4	-4	0
Improvement %	1	1	1	4	2	2	2	0

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	150	150	150	150	150	150	150	7
pull_request	150	150	150	150	150	150	150	7
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

parse canada.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	16	17	17	17	17	18	18	60
pull_request	16	17	17	17	17	18	18	59
Δ	0	0	0	0	0	0	0	-1
Improvement %	0	0	0	0	0	0	0	-1

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	133	134	134	134	134	134	134	60
pull_request	133	134	134	134	134	134	134	59
Δ	0	0	0	0	0	0	0	-1
Improvement %	0	0	0	0	0	0	0	-1

parse twitter.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	2644	2658	2664	2677	2691	2761	3351	367
pull_request	2592	2609	2617	2628	2652	2892	3405	374
Δ	-52	-49	-47	-49	-39	131	54	7
Improvement %	2	2	2	2	1	-5	-2	7

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	3138	3139	3139	3139	3139	3139	3139	367
pull_request	3138	3139	3139	3139	3139	3139	3139	374
Δ	0	0	0	0	0	0	0	7
Improvement %	0	0	0	0	0	0	0	7