[bug][fn] Prevent putstate uses empty values

[freeznet]

Fixes #22126

Main Issue: #xyz

PIP: #xyz

Motivation

When submitting the putstate requests with other libs such as pulsar-admin-go, the FunctionState JSON string may contain the default value of string or int, so the functions worker may use an incorrect value when the user submits with bytesString. See apache/pulsar-client-go#1184 for more details.

Modifications

• Fix the logic
• Add more tests

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository: freeznet#10

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 57.14286% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 73.57%. Comparing base (1b1cfb5) to head (ead47f6).
Report is 5 commits behind head on master.

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #22127       +/-   ##
=============================================
+ Coverage     34.05%   73.57%   +39.51%     
- Complexity    12150    32637    +20487     
=============================================
  Files          1659     1877      +218     
  Lines        129418   139528    +10110     
  Branches      14173    15307     +1134     
=============================================
+ Hits          44079   102660    +58581     
+ Misses        79497    28899    -50598     
- Partials       5842     7969     +2127     

Flag	Coverage Δ
inttests	24.58% <0.00%> (-0.17%)	⬇️
systests	24.24% <57.14%> (?)
unittests	72.86% <0.00%> (+40.99%)	⬆️

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

Files	Coverage Δ
...ulsar/functions/worker/rest/api/ComponentImpl.java	48.12% <57.14%> (+47.58%)	⬆️

... and 1522 files with indirect coverage changes