[lamarrr]

Replace the custom mutable-string and raw-storage device-view wrappers with operations on the core column device views. Add mutable_string_view for preallocated character storage and repr_element for loading and assigning stored representations.

Remove the column-type template argument from column_accessor and update kernel instantiations, checked arithmetic, URL examples, and the two existing preallocated-string tests. Reflect the underlying UDF value types separately from accessor tags, and accept PTX as an LTO binary format.

This PR is based on the reflection/storage-helper extraction. List types are not introduced here.

Validation

• Full libcudf build and all 122 CTest entries pass in the CUDA 13.3 devcontainer using sccache (sm_86).
• Focused accessor GPU probes and Compute Sanitizer memcheck pass with zero errors.
• Doxygen passes with warnings as errors.
• Python package builds and pytest suites were not run.

PR stack

Depends on #24425. List support follows in #24767. This draft targets main, so its PR diff includes that prerequisite until it merges. The changes specific to this part are in commit 650d45372d4794a7c5a265e2670b08dc1de58bcd and this comparison.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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