Support get mappers data without index/mapperids

[chaokunyang]

What do these changes do?

This PR removes source_idxes/source_mappers from FetchShuffle to reduce scheduling overhead of shuffle meta and make operands relying on those attributes work on ray task-based shuffle.

The core idea is:

• Remove source_idxes/source_mappers from FetchShuffle.
• Add source_idxes/source_mappers to mapper blocks if needed.
• Add chunk to context when executing operand so the operand mapper can get index and add it to mapper blocks.

Related issue number

Fixes #3186

Check code requirements

• [ ] tests added / passed (if needed)
• [ ] Ensure all linting tests pass, see here for how to run them