Validate timeout greater than 0s for InformersSyncTimeout

[marctc]

In early stages of Beyla Alloy integration this flag was set to 0 and Beyla was crashing.
This PR adds a validation (tho i wasn't able to replicate the error this time, so just in case).

Fixes #739

[grcevski]

LGTM!

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 73.56%. Comparing base (f632c99) to head (62a08b5).

Files	Patch %	Lines
pkg/beyla/config.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1103      +/-   ##
==========================================
+ Coverage   73.50%   73.56%   +0.06%     
==========================================
  Files         172      172              
  Lines       13091    13093       +2     
==========================================
+ Hits         9622     9632      +10     
+ Misses       2920     2911       -9     
- Partials      549      550       +1     

Flag	Coverage Δ
integration-test	51.00% <0.00%> (-0.04%)	⬇️
k8s-integration-test	52.99% <0.00%> (+0.12%)	⬆️
oats-test	33.72% <0.00%> (-0.01%)	⬇️
unittests	45.66% <0.00%> (-0.03%)	⬇️

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