Use clang-tidy on ebpf code

[rafaelroquetto]

This PR enables the use of clang-tidy to lint the code in the bpf/ directory. In a nutshell:

• Provide an initial .clang-tidy configuration. Not all checks are enabled at this time. Because it will take time to address the issues that come up when new checks are enabled, these will be done on a staggered fashion;
• Lint the current source code according to the current .clang-tidy configuration - the source files inside the bpf/ directory have been linted and adjusted to ensure the current checks pass. Files inside the headers/ directory are mostly ignored (specially vmlinux.h as they are both problematic and auto-generated.
• Enforce the linter rules by providing a workflow for clang-tidy. Because the vanilla clang-tidy package that ships with the runner is out of date (and unable to parse our configuration file), we fetch the latest clang binaries directly from the LLVM apt repositories.

Another PR will follow shortly documenting the usage of clang-format and clang-tidy on the README file.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.19%. Comparing base (cbca5fe) to head (74ec832).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1180      +/-   ##
==========================================
+ Coverage   81.12%   81.19%   +0.06%     
==========================================
  Files         136      136              
  Lines       11497    11497              
==========================================
+ Hits         9327     9335       +8     
+ Misses       1639     1633       -6     
+ Partials      531      529       -2     

Flag	Coverage Δ
integration-test	57.02% <ø> (+0.02%)	⬆️
k8s-integration-test	58.93% <ø> (+0.12%)	⬆️
oats-test	35.82% <ø> (-0.07%)	⬇️
unittests	53.33% <ø> (+<0.01%)	⬆️

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[grcevski]

LGTM! Nice!