selftests/bpf: Test bpf_sock_destroy

The test cases for destroying sockets mirror the intended usages of the
bpf_sock_destroy kfunc using iterators.

The destroy helpers set `ECONNABORTED` error code that we can validate
in the test code with client sockets. But UDP sockets have an overriding
error code from `disconnect()` called during abort, so the error code
validation is only done for TCP sockets.

The failure test cases validate that the `bpf_sock_destroy` kfunc is not
allowed from program attach types other than BPF trace iterator, and
such programs fail to load.

Signed-off-by: Aditi Ghag <aditi.ghag@isovalent.com>
Link: https://lore.kernel.org/r/20230519225157.760788-10-aditi.ghag@isovalent.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>