Light refactoring of the TC attachment code

[rafaelroquetto]

This PR introduces a light refactoring of the TC attachment code, in order to enable it to be reused between the tracers and netolly. The key changes are:

• Break WatchAndRegisterTC into multiple atomic functions, that allow them to be used by the netolly flow tracer
• Parameterise the TC attachment handles and names
• Use unique handles for different classes of TC programs, in order to avoid collisions with ourselves or third parties (such as cilium) - the handles follow the format 0xb31N.

Ideally I would have liked to collapse the code gap between the tracers and netolly even more, but that would entail a larger refactoring that requires further discussion, involving sharing the interface informers and registers, so that the interface name cache inside the registerer can be shared. I've thus opted for the pragmatic approach, which translates on sharing the core attachment, qdisc creation and cleanup code, as well as the main watcher loop.

[codecov]

Codecov Report

Attention: Patch coverage is 70.21277% with 28 lines in your changes missing coverage. Please review.

Project coverage is 81.32%. Comparing base (5770689) to head (882f3e1).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/internal/netolly/ebpf/tracer.go	57.14%	10 Missing and 5 partials ⚠️
pkg/internal/ebpf/common/tc_linux.go	72.34%	10 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1466      +/-   ##
==========================================
+ Coverage   81.11%   81.32%   +0.21%     
==========================================
  Files         149      149              
  Lines       15342    15253      -89     
==========================================
- Hits        12444    12404      -40     
+ Misses       2281     2244      -37     
+ Partials      617      605      -12     

Flag	Coverage Δ
integration-test	59.77% <70.21%> (+0.07%)	⬆️
k8s-integration-test	60.73% <70.21%> (+0.10%)	⬆️
oats-test	34.02% <0.00%> (+0.19%)	⬆️
unittests	52.11% <2.12%> (+0.34%)	⬆️

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[grcevski]

LGTM!