Add rewrite context to MV cost function

[xudong963]

Summary

• add rewrite context metadata for candidate selection in view exploitation
• pass source table refs from logical rewrite into OneOf and OneOfExec
• extend CostFn to receive cost context and add tests covering context propagation

Validation

• cargo fmt --all
• CARGO_INCREMENTAL=0 cargo check --tests
• cargo test --lib rewrite::exploitation -- --nocapture (linking failed due to local disk space: errno=28)

[zhuqi-lucas]

LGTM