fix(telemetry): Handle empty configuration payload properly

[dmehala]

Description

This fix addresses two issues:

1. Prevents invalid telemetry payloads when there are no configuration entries.
2. Ensures configuration updates are correctly processed and not carried over to the next update.

Motivation

Additional Notes

Jira ticket: [PROJ-IDENT]

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 62.50000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 93.78%. Comparing base (ccbbae9) to head (1d16fca).

Files with missing lines	Patch %	Lines
src/datadog/datadog_agent.cpp	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #186      +/-   ##
==========================================
- Coverage   93.80%   93.78%   -0.02%     
==========================================
  Files          73       73              
  Lines        4195     4199       +4     
==========================================
+ Hits         3935     3938       +3     
- Misses        260      261       +1     

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