…rrow errors (#1253)

* Refactor schema, config, dataframe, and expression classes to use RwLock and Mutex for interior mutability

* Add error handling to CaseBuilder methods to preserve builder state

* Refactor to use parking_lot for interior mutability in schema, config, dataframe, and conditional expression modules

* Add concurrency tests for SqlSchema, Config, and DataFrame

* Add tests for CaseBuilder to ensure builder state is preserved on success

* Add test for independent handles in CaseBuilder to verify behavior

* Fix CaseBuilder to preserve state correctly in when() method

* Refactor to use named constant for boolean literals in test_expr.py

* fix ruff errors

* Refactor to introduce type aliases for cached batches in dataframe.rs

* Cherry pick from #1252

* Add most expr - cherry pick from #1252

* Add source root - cherry pick #1252

* Fix license comment formatting in config.rs

* Refactor caching logic to use a local variable for IPython environment check

* Add test for ensuring exposed pyclasses default to frozen

* Add PyO3 class mutability guidelines reference to contributor guide

* Mark boolean expression classes as frozen for immutability

* Refactor PyCaseBuilder methods to eliminate redundant take/store logic

* Refactor PyConfig methods to improve readability by encapsulating configuration reads

* Resolve patch apply conflicts for CaseBuilder concurrency improvements

- Added CaseBuilderHandle guard that keeps the underlying CaseBuilder alive while holding the mutex and restores it on drop
- Updated when, otherwise, and end methods to operate through the guard and consume the builder explicitly
- This prevents transient None states during concurrent access and improves thread safety

* Resolve Config optimization conflicts for improved read/write concurrency

- Released Config read guard before converting values to Python objects in get and get_all
- Ensures locks are held only while collecting scalar entries, not during expensive Python object conversion
- Added regression test that runs Config.get_all and Config.set concurrently to guard against read/write contention regressions
- Improves overall performance by reducing lock contention in multi-threaded scenarios

* Refactor PyConfig get methods for improved readability and performance

* Refactor test_expr.py to replace positional boolean literals with named constants for improved linting compliance

* fix ruff errors

* Add license header to test_pyclass_frozen.py for compliance

* Alternate approach to case expression

* Replace case builter with keeping the expressions and then applying as required

* Update unit tests

* Refactor case and when functions to utilize PyCaseBuilder for improved clarity and functionality

* Update src/expr/conditional_expr.rs

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Co-authored-by: ntjohnson1 <24689722+ntjohnson1@users.noreply.github.com>
Co-authored-by: Tim Saucer <timsaucer@gmail.com>