Improve LSM support autodetection

[MatteoNardi]

Improve LSM autodetection by trying to load an example LSM program.

• split bpf-builder to its own crate because bpf-common would have needed to depend on itself at build-time.
• added lsm_supported to BpfContext in order to avoid repeating the time-consuming check.
• add a configuration field to pulsar for forcing the use of kprobes/lsm

I have

• run cargo fmt;
• run cargo clippy;
• run cargo testand all tests pass;
• linked to the originating issue (if applicable).

[MatteoNardi]

I advise to review commit by commit since the first one contains a lot of moved files.

A few notes:

• I haven't added a CLI option in test-suite to override LSM autodetection. Since libtest_mimic does its own arguments parsing and it's a feature we don't really need, I don't think the extra complexity is justified.
• The test-suite needs a blocking version of lsm_supported() so in async contexts I've wrapped it with spawn_blocking. Maybe I could have exposed two functions pub lsm_supported() and pub blocking_lsm_supported()

[banditopazzo]

apart few minor things looks good to me