Avoided redundant checks in creating an Utf8Array from MutableUtf8Array

[jorgecarleitao]

This PR fixes a performance issue when creating Utf8Array from MutableUtf8Array: since MutableUtf8Array has the same invariants as Utf8Array, we can use from_data_unchecked, avoiding re-running expensive utf8 validation.

[codecov]

Codecov Report

Merging #560 (a4a4369) into main (5fc843d) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #560      +/-   ##
==========================================
- Coverage   78.92%   78.89%   -0.04%     
==========================================
  Files         382      382              
  Lines       24276    24534     +258     
==========================================
+ Hits        19160    19356     +196     
- Misses       5116     5178      +62     

Impacted Files	Coverage Δ
src/array/utf8/mutable.rs	85.25% <100.00%> (ø)
src/io/ipc/read/array/union.rs	70.49% <0.00%> (-4.51%)	⬇️
src/array/union/mod.rs	79.27% <0.00%> (-0.34%)	⬇️
tests/it/array/mod.rs	100.00% <0.00%> (ø)
src/array/display.rs	53.47% <0.00%> (+2.37%)	⬆️
src/datatypes/mod.rs	81.65% <0.00%> (+4.03%)	⬆️
src/io/avro/read/mod.rs	86.95% <0.00%> (+4.60%)	⬆️
src/io/json_integration/schema.rs	51.65% <0.00%> (+5.59%)	⬆️
src/io/ipc/read/array/fixed_size_binary.rs	57.69% <0.00%> (+10.07%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5fc843d...a4a4369. Read the comment docs.