doc: Update Safe Transaction Service sections

[falvaradorodriguez]

Closes https://github.com/safe-global/safe-transaction-service/issues/1783.

[github-actions[bot]]

Overall readability score: 57.06 (🟢 +0.82)

File	Readability
api-overview.md	47.31 (🔴 -5)
api-safe-transaction-service.mdx	50.76 (🔴 -0.09)
api-rpc-requirements.md	59.59 (-)
faq.md	46.96 (-)
delegates.mdx	16.3 (🟢 +0)
transaction-service-overview.mdx	44.56 (🟢 +0.37)

View detailed metrics

🟢 - Shows an increase in readability 🔴 - Shows a decrease in readability

File	Readability	FRE	GF	ARI	CLI	DCRS
api-overview.md	47.31	37.71	10.83	14.3	15.19	7.73
	🔴 -5	🔴 -2.33	🔴 -1.16	🔴 -1.1	🔴 -0.23	🔴 -0.22
api-safe-transaction-service.mdx	50.76	38.62	9.8	14.4	15.25	7.18
	🔴 -0.09	🔴 -0.61	🔴 -0.22	🟢 +0.1	🟢 +0.17	🟢 +0
api-rpc-requirements.md	59.59	54.02	10.54	12.2	11.71	7.38
	-	-	-	-	-	-
faq.md	46.96	50.06	13.07	14.3	12.59	8.42
	-	-	-	-	-	-
delegates.mdx	16.3	0	13.13	22	19	9.06
	🟢 +0	🟢 +0	🟢 +0	🟢 +0	🟢 +0	🟢 +0
transaction-service-overview.mdx	44.56	42.51	12.44	15.7	13.87	7.92
	🟢 +0.37	🟢 +0	🟢 +0	🔴 -0.1	🟢 +0	🟢 +0.16

Averages:

	Readability	FRE	GF	ARI	CLI	DCRS
Average	57.06	49.79	10.62	12.46	12.25	7.55
	🟢 +0.82	🟢 +0.79	🟢 +0.12	🟢 +0.15	🟢 +0.09	🟢 +0.04

View metric targets

Metric	Range	Ideal score
Flesch Reading Ease	100 (very easy read) to 0 (extremely difficult read)	60
Gunning Fog	6 (very easy read) to 17 (extremely difficult read)	8 or less
Auto. Read. Index	6 (very easy read) to 14 (extremely difficult read)	8 or less
Coleman Liau Index	6 (very easy read) to 17 (extremely difficult read)	8 or less
Dale-Chall Readability	4.9 (very easy read) to 9.9 (extremely difficult read)	6.9 or less

[falvaradorodriguez]

To be considered:

• These changes had been intended by the Core API team for the existing structure previously. Feel free to change anything that is not in the right place.

• It has been very complicated to rethink the services diagram in mermaid, so it is kept in PNG.

~~In the new "API" overview section there is a "Reference" section that has a broken link to "/core-api/transaction-service-reference". Where should it lead us?~~

[github-actions[bot]]

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https://update_safe_core_doc--docs.review.5afe.dev