Catergorise the CI workflows

[Kailai-Wang]

Context

We are having more and more workflows. Maybe it makes sense to sort and group them for better management and views. A common way is prefixing it with some pre-defined category numbers, e.g. 000-x-y-z.yml, 001-x-y-z.xml

We can have a README to list and explain the categories, e.g.

numbers	aims
000	GHA helpers
001	Parachain helpers
002	TEE-worker helpers
...	...

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✔️ Please set appropriate labels and assignees if applicable.

[Kailai-Wang]

Still valid, but we haven't got time to do this.