Ensure TC programs play nice with 3rdparty programs

[rafaelroquetto]

We need to ensure we play nice with third-parties also using tc, by not accidentally removing their programs. That is achieved by:

• if a qdisc already exists, don't try to delete it - reuse it instead
• during tear down, do not delete any qdiscs that are not empty after removing our own programs from it
• ensure our filters return TC_ACT_UNSPEC so that they don't consume any packets
• "namespaced" our ebpf programs with the beyla_ prefix - not entirely necessary here, but perhaps a good idea anyway to avoid any potential collisions

[codecov]

Codecov Report

Attention: Patch coverage is 90.47619% with 16 lines in your changes missing coverage. Please review.

Project coverage is 81.12%. Comparing base (cc8de1b) to head (f422f93).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/internal/ebpf/common/tc_linux.go	64.86%	7 Missing and 6 partials ⚠️
pkg/internal/netolly/ebpf/tracer.go	50.00%	0 Missing and 2 partials ⚠️
pkg/internal/netolly/ebpf/sock_tracer.go	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1462      +/-   ##
==========================================
- Coverage   81.16%   81.12%   -0.05%     
==========================================
  Files         149      149              
  Lines       15321    15339      +18     
==========================================
+ Hits        12436    12444       +8     
- Misses       2271     2279       +8     
- Partials      614      616       +2     

Flag	Coverage Δ
integration-test	59.66% <90.47%> (-0.05%)	⬇️
k8s-integration-test	60.63% <90.47%> (+0.02%)	⬆️
oats-test	33.81% <69.04%> (-0.05%)	⬇️
unittests	51.80% <0.00%> (-0.07%)	⬇️

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[grcevski]

LGTM! I'd merge this in if tests pass. We can follow-up with k8s test with Cilium, docs on how to run with Cilium etc.