Avoid decoding unneeded values in ByteArrayDecoderDictionary

[thinkharderdev]

Which issue does this PR close?

Closes #2088

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

[codecov-commenter]

Codecov Report

Merging #2154 (b340d55) into master (1621c71) will decrease coverage by 0.01%.
The diff coverage is 44.44%.

@@            Coverage Diff             @@
##           master    #2154      +/-   ##
==========================================
- Coverage   82.85%   82.83%   -0.02%     
==========================================
  Files         237      237              
  Lines       61381    61381              
==========================================
- Hits        50856    50846      -10     
- Misses      10525    10535      +10     

Impacted Files	Coverage Δ
parquet/src/arrow/array_reader/byte_array.rs	85.79% <44.44%> (ø)
...rquet/src/arrow/record_reader/definition_levels.rs	84.38% <0.00%> (-3.38%)	⬇️
arrow/src/datatypes/datatype.rs	62.69% <0.00%> (-0.32%)	⬇️
parquet_derive/src/parquet_field.rs	65.75% <0.00%> (-0.23%)	⬇️

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[ursabot]

Benchmark runs are scheduled for baseline = 73153fe and contender = bd65d59. bd65d59 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java