feat: upgrade Spring to v6, SpringBoot to v3

[bednar]

Closes #649

Proposed Changes

Migrate influxdb-spring from Spring Boot v2 to v3, Spring to v6.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• mvn test completes successfully
• Commit messages are conventional
• Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (50e1142) 88.35% compared to head (41e8650) 88.33%.

❗ Current head 41e8650 differs from pull request most recent head 82547fb. Consider uploading reports for the commit 82547fb to get more accurate results

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Additional details and impacted files

@@             Coverage Diff              @@
##             master     #673      +/-   ##
============================================
- Coverage     88.35%   88.33%   -0.03%     
- Complexity      777      779       +2     
============================================
  Files           173      173              
  Lines          7078     7078              
  Branches        393      389       -4     
============================================
- Hits           6254     6252       -2     
  Misses          699      699              
- Partials        125      127       +2     

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[karel-rehor]

Added a test change here. Jakub, does this work for you? Does it not defeat Utku Aydin's intent for this assertion?

[karel-rehor]

This looks OK. To check the build of this branch locally I added a change to WriteApiTest.userAgent():1004-1025. If this change does not negatively impact earlier intentions for this test, I think this PR can be merged.