Replace self-hosted CI runners with GitHub-hosted ones

[qdeslandes]

The CI uses self-hosted runners because when the CI workflow was created, GitHub-hosted runner didn't comply with the following requirements:

• Run on Linux 6.4+: only Ubuntu 22.04 was available, running on an old Linux kernel.
• Support arm64 runners: while GitHub has provided arm64 runners for some time now, they run on Apple Silicon, which doesn't allow for nested virtualization, thus preventing Docker from being used.

Lately, GitHub fixed both of those blockers as it provides arm64 runners on Ubuntu 24.04 for Team and Enterprise Cloud plans, which makes those available to bpfilter through the Facebook org.

Self-hosted runners come with some maintenance that we should avoid if we can, and bpfilter's CI should be modified to use the GitHub runners instead of the self-hosted ones.

Tests have been conducted to validate the viability of the self-hosted runners, especially when it comes to the usage of BPF_PROG_TEST_RUN (see better_ci branch). To benefit from the arm64 Ubuntu runners, the development, and tests must be performed on the main repository, meaning people without writing rights can't contribute to this task.