Create 'CodableSupport' trait for embedded

[dduan]

CodableSupport is a trait that's by default enabled. The Codable related APIs are enabled by this trait. When this trait is not enabled, the lower level parsing API remain available, and that portion must not depend on Foundation. All the stand test should pass for non-CodableSupport potion of the library. The non-CodableSupport APIs should function for embedded Swift.

Few things needs to happen before this gets merged:

• A reliable CI check for running tests without the default trait
• A CI build for embedded Swift of the non-CodableSupport part
• Documentation updates:
  • A mention of embedded support in introductory materials
  • An explanation of the trait
  • Per API annotation about availability for embeded (or trait membership?)
  • A dedicated article for embeded.
  • developer docs
  • change log updates
• An test on an actual embeded device :)

Closes #232
Closes #227

[github-actions]

Comparing results between 'main' and 'pull_request'

Host 'runnervmwffz4' 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	70	71	71	74	81	98	150	6976
pull_request	70	71	71	74	80	98	165	6964
Δ	0	0	0	0	-1	0	15	-12
Improvement %	0	0	0	0	1	0	-10	-12

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

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	860	860	860	860	860	860	860	6976
pull_request	859	859	859	860	860	860	860	6964
Δ	-1	-1	-1	0	0	0	0	-12
Improvement %	0	0	0	0	0	0	0	-12

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	4778	4879	4919	4963	5111	8047	25869	10000
pull_request	4859	4979	5019	5071	5191	7947	41998	10000
Δ	81	100	100	108	80	-100	16129	0
Improvement %	-2	-2	-2	-2	-2	1	-62	0

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

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	11	12	12	12	12	12	12	10000
pull_request	10	11	11	11	11	11	11	10000
Δ	-1	-1	-1	-1	-1	-1	-1	0
Improvement %	9	8	8	8	8	8	8	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	262	263	265	265	268	268	268	4
pull_request	263	263	266	267	267	267	267	4
Δ	1	0	1	2	-1	-1	-1	0
Improvement %	0	0	0	-1	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	9652	9708	9740	9765	9839	13787	16520	100
pull_request	9564	9609	9650	9699	9757	10174	10245	103
Δ	-88	-99	-90	-66	-82	-3613	-6275	3
Improvement %	1	1	1	1	1	26	38	3

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

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	114	114	114	114	114	114	114	100
pull_request	114	114	114	114	114	114	114	103
Δ	0	0	0	0	0	0	0	3
Improvement %	0	0	0	0	0	0	0	3

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	133	133	133	133	136	136	136	8
pull_request	142	146	148	150	150	150	150	7
Δ	9	13	15	17	14	14	14	-1
Improvement %	-7	-10	-11	-13	-10	-10	-10	-1

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

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	188	188	188	188	188	188	188	8
pull_request	188	188	188	188	188	188	188	7
Δ	0	0	0	0	0	0	0	-1
Improvement %	0	0	0	0	0	0	0	-1

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	16	16	17	17	18	18	61
pull_request	17	17	17	17	18	19	19	59
Δ	1	1	1	0	1	1	1	-2
Improvement %	-6	-6	-6	0	-6	-6	-6	-2

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

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	131	132	132	132	132	132	132	61
pull_request	130	131	131	131	131	131	131	59
Δ	-1	-1	-1	-1	-1	-1	-1	-2
Improvement %	1	1	1	1	1	1	1	-2

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	2232	2253	2263	2275	2292	2392	3024	431
pull_request	2265	2284	2292	2306	2324	2384	2836	425
Δ	33	31	29	31	32	-8	-188	-6
Improvement %	-1	-1	-1	-1	-1	0	6	-6

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

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	3757	3758	3758	3758	3758	3758	3758	431
pull_request	3756	3757	3757	3757	3757	3757	3757	425
Δ	-1	-1	-1	-1	-1	-1	-1	-6
Improvement %	0	0	0	0	0	0	0	-6