Add fixed-size binary support #6618

Job	Run time
Rust/C++ FFI tests (asan)	1s
C++ API (coverage)	1s
Rust tests (miri)	1s
Rust tests (tsan)	1s
Rust tests (asan)	1s
Mirror DuckDB to R2 / Resolve DuckDB version and check R2	1s
Mirror DuckDB to R2 / Mirror DuckDB ${{ matrix.archive }} to R2	1s
DuckDB libraries available in R2	1s
Rust tests (coverage) (${{ matrix.suite }})	1s
Rust/C++ FFI tests (tsan)	2s
	11s

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