Avoid sending empty profiles

[stefanosiano]

📜 Description

Added a check on the sampled profile not to be empty in order to be sent

💡 Motivation and Context

We received few profiles without any content. There is already a check if the profiling trace file doesn't exists or cannot be read, but no check if it is empty. I couldn't be able to reproduce the issue, other than changing the content of the file right before being sent.
However, this should fix it

💚 How did you test it?

I added both a Unit and a Ui test to check empty profiles are discarded

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the docs if needed
• No breaking changes

[codecov-commenter]

Codecov Report

Base: 80.62% // Head: 80.64% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (695ead7) compared to base (0d55590).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2232      +/-   ##
============================================
+ Coverage     80.62%   80.64%   +0.01%     
- Complexity     3357     3358       +1     
============================================
  Files           240      240              
  Lines         12335    12337       +2     
  Branches       1638     1639       +1     
============================================
+ Hits           9945     9949       +4     
+ Misses         1783     1782       -1     
+ Partials        607      606       -1     

Impacted Files	Coverage Δ
...ry/src/main/java/io/sentry/SentryEnvelopeItem.java	87.58% <100.00%> (+0.17%)	⬆️
...n/java/io/sentry/transport/ReusableCountLatch.java	94.11% <0.00%> (+5.88%)	⬆️

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