fix: added type validation for inner_config in deserialize_keras_object (#22974)

* fix: added type validation for inner_config in deserialize_keras_object

Includes type validation for standard classes, __typespec__ and functions as well as an exception for Sequential models. Also added corresponding unit tests to serialization_lib_test.

* Update keras/src/saving/serialization_lib.py

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* "refactor: remove redundant check for inner_config, as suggested"

* Update keras/src/saving/serialization_lib.py

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* Update keras/src/saving/serialization_lib.py

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* Fix indentation and formatting in serialization_lib.py

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Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: hertschuh <1091026+hertschuh@users.noreply.github.com>