Add fixed-size binary support #6619

Job	Run time
Rust tests (miri)	1m 35s
Rust tests (asan)	6m 59s
Rust/C++ FFI tests (tsan)	1m 55s
Rust/C++ FFI tests (asan)	2m 21s
C++ API (coverage)	1m 16s
Rust tests (tsan)	6m 49s
Mirror DuckDB to R2 / Resolve DuckDB version and check R2	7s
DuckDB libraries available in R2	2s
Mirror DuckDB to R2 / Mirror DuckDB ${{ matrix.archive }} to R2	-1s
Rust tests (coverage) (tests)	6m 44s
	27m 47s

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