Optimize dateTimeConvert scalar function to only parse the format once

[Jackie-Jiang]

Make dateTimeConvert scalar function stateful so that the format is parsed only once across multiple invocations. The state is persisted within the scope of FunctionInvoker, so multiple functions with the same name won't share the same state.

[codecov-commenter]

Codecov Report

Merging #8939 (e103485) into master (09fcdd5) will decrease coverage by 44.77%.
The diff coverage is 0.00%.

@@              Coverage Diff              @@
##             master    #8939       +/-   ##
=============================================
- Coverage     69.69%   24.92%   -44.78%     
+ Complexity     4630       47     -4583     
=============================================
  Files          1813     1802       -11     
  Lines         94521    94171      -350     
  Branches      14116    14078       -38     
=============================================
- Hits          65879    23469    -42410     
- Misses        24033    68416    +44383     
+ Partials       4609     2286     -2323     

Flag	Coverage Δ
integration1	?
integration2	24.92% <0.00%> (+0.05%)	⬆️
unittests1	?
unittests2	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
.../pinot/common/function/scalar/DateTimeConvert.java	0.00% <0.00%> (ø)
...inot/common/function/scalar/DateTimeFunctions.java	6.25% <ø> (-88.99%)	⬇️
...in/java/org/apache/pinot/spi/utils/StringUtil.java	0.00% <0.00%> (-100.00%)	⬇️
.../java/org/apache/pinot/spi/utils/BooleanUtils.java	0.00% <0.00%> (-100.00%)	⬇️
...java/org/apache/pinot/spi/trace/BaseRecording.java	0.00% <0.00%> (-100.00%)	⬇️
...java/org/apache/pinot/spi/trace/NoOpRecording.java	0.00% <0.00%> (-100.00%)	⬇️
...ava/org/apache/pinot/spi/config/table/FSTType.java	0.00% <0.00%> (-100.00%)	⬇️
...ava/org/apache/pinot/spi/config/user/RoleType.java	0.00% <0.00%> (-100.00%)	⬇️
...ava/org/apache/pinot/spi/data/MetricFieldSpec.java	0.00% <0.00%> (-100.00%)	⬇️
...java/org/apache/pinot/common/tier/TierFactory.java	0.00% <0.00%> (-100.00%)	⬇️
... and 1328 more

---

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 5b2b4aa...e103485. Read the comment docs.