feat(cudf): Support map construction and element lookup

[winningsix]

Summary

• add cuDF support for map construction from alternating key/value expressions
• represent map columns as LIST<STRUCT<K,V>> and preserve sliced offsets and parent validity
• route Spark and Presto element_at map lookups through cuDF
• support literal and column keys, return null for missing keys, and preserve null map/key semantics
• keep unsupported key/value shapes fail closed

Testing

• added GPU selection coverage for literal and column map keys
• added Spark expression parity coverage for map construction, present/missing keys, null values, and dynamic keys
• clang-format 18.1.8 validation

[sperlingxx]

Plz fix the format issues

Run pre-commit run --show-diff-on-failure --color=always --all-files
2m 19s
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[thirtiseven]

Blocking: this preserves duplicate keys, while the Spark CPU MapFunction either applies LAST_WIN or throws when throw_exception_on_duplicate_map_keys is enabled. Since the new map lookup uses FIND_FIRST, element_at(map("k", c0, "k", c1), "k") returns c0 on GPU but c1 on CPU. Please implement the same duplicate-key policy (including the exception mode), or fail GPU selection when uniqueness cannot be guaranteed, and add literal/dynamic duplicate-key parity tests.