Speed up HTTP2 check

[grcevski]

This PR adds a quick check for missed HTTP2 connections before we try to use the frame parser from Go. This reduces Beyla's CPU usage on the OTel demo from 25% to less than 3%.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.61538% with 6 lines in your changes missing coverage. Please review.

Project coverage is 61.52%. Comparing base (e406a94) to head (eed7f1b).
Report is 1 commits behind head on main.

Files	Patch %	Lines
pkg/internal/ebpf/common/http2grpc_transform.go	89.18%	2 Missing and 2 partials ⚠️
pkg/internal/ebpf/common/tcp_detect_transform.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #923       +/-   ##
===========================================
- Coverage   78.92%   61.52%   -17.41%     
===========================================
  Files         131      131               
  Lines        9862     9945       +83     
===========================================
- Hits         7784     6119     -1665     
- Misses       1572     3393     +1821     
+ Partials      506      433       -73     

Flag	Coverage Δ
integration-test	?
k8s-integration-test	?
oats-test	35.31% <46.15%> (-0.24%)	⬇️
unittests	45.41% <79.48%> (+0.49%)	⬆️

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[mariomac]

Amazing