[GOBBLIN-1853] Reduce # of Hive calls during schema related updates in metadata registration

[homatthew]

Dear Gobblin maintainers,

Please accept this PR. I understand that it will not be reviewed until I have checked off all the steps below!

JIRA

• My PR addresses the following Gobblin JIRA issues and references them in the PR title. For example, "[GOBBLIN-XXX] My Gobblin PR"
  • https://issues.apache.org/jira/browse/GOBBLIN-XXX

Description

• Here are some details about my PR, including screenshots (if applicable):
  The HiveMetadataWriter and IcebergMetadataWriter make schema changes and need to make calls to Hive / HDFS per GMCE. This is an unnecessary hotspot because we can reference the schema cache beforehand and determine whether we actually need to make network call.

Also, there are cases where the HiveMetadataWriter can update the latest schema to be a null schema. We want to fail earlier, and fail the code when updating the latest schema map instead of failing later with a NPE. I've also changed the if statement from containsKey to checking if the value is null so that if this somehow happens in the future, we do not try to update the table with a null schema which would cause a NPE

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference JIRA issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

[homatthew]

original import ordering did not comply with Apache Gobblin OSS style guide

[ZihanLi58]

+1 LGTM, thanks for the fix

[codecov-commenter]

Codecov Report

Merging #3716 (b8b5c87) into master (2c2ffac) will increase coverage by 0.15%.
The diff coverage is 5.88%.

@@             Coverage Diff              @@
##             master    #3716      +/-   ##
============================================
+ Coverage     46.79%   46.95%   +0.15%     
- Complexity    10793    10821      +28     
============================================
  Files          2143     2143              
  Lines         84528    84600      +72     
  Branches       9392     9404      +12     
============================================
+ Hits          39557    39721     +164     
+ Misses        41360    41255     -105     
- Partials       3611     3624      +13     

Impacted Files	Coverage Δ
...apache/gobblin/hive/writer/HiveMetadataWriter.java	0.00% <0.00%> (ø)
.../gobblin/iceberg/writer/IcebergMetadataWriter.java	70.45% <20.00%> (-0.49%)	⬇️

... and 9 files with indirect coverage changes

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