FFI: get scalars from arrays #6606

Job	Run time
Rust/C++ FFI tests (tsan)	7m 1s
Rust/C++ FFI tests (asan)	2m 10s
Rust tests (tsan)	6m 37s
C++ API (coverage)	7m 1s
Rust tests (miri)	7m 1s
Rust tests (asan)	7m 0s
Mirror DuckDB to R2 / Resolve DuckDB version and check R2	5s
Mirror DuckDB to R2 / Mirror DuckDB ${{ matrix.archive }} to R2	-1s
DuckDB libraries available in R2	2s
Rust tests (coverage) (tests)	6m 29s
	43m 25s

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