Add more validations for upserts

[KKcorps]

• Do not allow users to change primary key columns
• Check if snapshot is enabled already if preload is enabled

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 37.50000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 62.01%. Comparing base (59551e4) to head (119bc06). Report is 1778 commits behind head on master.

Files with missing lines	Patch %	Lines
...rc/main/java/org/apache/pinot/spi/data/Schema.java	33.33%	2 Missing and 2 partials :warning:
...he/pinot/segment/local/utils/TableConfigUtils.java	50.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #12686      +/-   ##
============================================
+ Coverage     61.75%   62.01%   +0.26%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2461      +25     
  Lines        133233   134745    +1512     
  Branches      20636    20822     +186     
============================================
+ Hits          82274    83566    +1292     
- Misses        44911    45033     +122     
- Partials       6048     6146      +98     

Flag	Coverage Δ
custom-integration1	<0.01% <0.00%> (-0.01%)	:arrow_down:
integration	<0.01% <0.00%> (-0.01%)	:arrow_down:
integration1	<0.01% <0.00%> (-0.01%)	:arrow_down:
integration2	0.00% <0.00%> (ø)
java-11	61.97% <37.50%> (+0.26%)	:arrow_up:
java-21	61.86% <37.50%> (+0.24%)	:arrow_up:
skip-bytebuffers-false	62.00% <37.50%> (+0.26%)	:arrow_up:
skip-bytebuffers-true	61.82% <37.50%> (+34.10%)	:arrow_up:
temurin	62.01% <37.50%> (+0.26%)	:arrow_up:
unittests	62.01% <37.50%> (+0.26%)	:arrow_up:
unittests1	46.74% <25.00%> (-0.15%)	:arrow_down:
unittests2	27.98% <12.50%> (+0.25%)	:arrow_up:

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[Jackie-Jiang]

Not sure if we want to prevent user from changing primary keys. If there is no snapshot, changing primary key should be okay