[feature] Cache Key Customization

[zzmao]

Feature Area

/area backend
/area sdk

What feature would you like to see?

Setting custom cache key at the task level

What is the use case or pain point?

Currently, the cache key in KFP is generated internally, and users are unable to customize or set it.
However, some users have expressed the need for more granular control over caching behavior by setting custom cache keys at the task level.

Is there a workaround currently?

N/A

Proposal:

https://docs.google.com/document/d/1oNgYyFYondaVSFf9Pd3Q9uVzaqBr5wrOMHKgX9MMa78/edit?tab=t.0

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