Added support for FFI of dictionary-encoded arrays

[jorgecarleitao]

out of abundance of caution, I have also ran cargo valgrind test --lib --no-default-features, which runs the tests behind valgrind, to make sure no memory leaks are detected.

[codecov]

Codecov Report

Merging #267 (f774364) into main (bfb4910) will increase coverage by 0.16%.
The diff coverage is 63.43%.

@@            Coverage Diff             @@
##             main     #267      +/-   ##
==========================================
+ Coverage   77.37%   77.53%   +0.16%     
==========================================
  Files         232      234       +2     
  Lines       20108    20207      +99     
==========================================
+ Hits        15558    15668     +110     
+ Misses       4550     4539      -11     

Impacted Files	Coverage Δ
src/array/boolean/ffi.rs	0.00% <0.00%> (ø)
src/array/dictionary/mod.rs	65.00% <ø> (+5.90%)	⬆️
src/array/mod.rs	53.15% <ø> (ø)
src/array/ffi.rs	43.24% <33.33%> (+8.10%)	⬆️
src/array/struct_.rs	49.18% <50.00%> (ø)
src/ffi/schema.rs	61.53% <61.53%> (ø)
src/ffi/array.rs	80.00% <64.70%> (-3.53%)	⬇️
src/array/dictionary/ffi.rs	75.00% <75.00%> (ø)
src/ffi/ffi.rs	86.45% <86.36%> (+15.91%)	⬆️
src/array/binary/ffi.rs	81.81% <100.00%> (ø)
... and 6 more

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