Move TaskContext to DataFusion execution without SessionConfig

[alamb]

Draft as builds on #5580

Which issue does this PR close?

Part of #1754

Rationale for this change

I am trying to extract the physical_plan code into its own crate; and to do so I need to remove the circular dependencies between core --> datasource --> execution --> datasource

The TaskContext is the part of the SessionState that is used at runtime, so I want it it into the datafusion_execution crate.

See more details in #1754 (comment)

What changes are included in this PR?

1. Move TaskContext to datafusion_execution
2. Change session_config: SessionConfig, field to its two fields extensions and config_options

Are these changes tested?

Covered by existing tests

Are there any user-facing changes?

Yes, anyone who uses SessionConfig in their execution plans will have to update their code to use config_options or extensions directly.

I am worried that this is too much API churn (though I think the resulting API is cleaner). I also have a PR to move SessionConfig into datafusion_execution.
#5581