Added MutableUtf8Array::extend_values

[ritchie46]

MutableUtf8Array already has Extend for iterators over Option<S: AsRef<str> and iterators over values and optional values from trusted length iterators, but not yet a method for iterators over values whose length cannot be trusted.

This PR adds that.

[codecov]

Codecov Report

Merging #798 (b50ac47) into main (777f375) will increase coverage by 0.02%.
The diff coverage is 95.45%.

@@            Coverage Diff             @@
##             main     #798      +/-   ##
==========================================
+ Coverage   71.50%   71.53%   +0.02%     
==========================================
  Files         321      321              
  Lines       16739    16755      +16     
==========================================
+ Hits        11970    11986      +16     
  Misses       4769     4769              

Impacted Files	Coverage Δ
src/array/utf8/mutable.rs	80.45% <90.90%> (-0.02%)	⬇️
src/array/physical_binary.rs	98.09% <100.00%> (+0.22%)	⬆️
src/io/parquet/read/nested_utils.rs	78.43% <0.00%> (+0.98%)	⬆️

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