Tests: Use a real program section in return, var_rval and if

These three declared @section("sometag1"), which is not a section name libbpf
can map to a program type:

    libbpf: failed to guess program type from ELF section 'sometag1'

so they were rejected before the kernel verifier ever saw them. They generate
IR and compile fine; only the section was wrong. Switch to
tracepoint/syscalls/sys_enter_execve, matching the other tracepoint tests.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: r41k0u

tests/failing_tests/if.py

@@ -3,7 +3,7 @@
 
 
 @bpf
-@section("sometag1")
+@section("tracepoint/syscalls/sys_enter_execve")
 def sometag(ctx: c_void_p) -> c_int64:
     if 3 + 2 == 5:
         return c_int64(5)

tests/passing_tests/return.py

@@ -3,7 +3,7 @@
 
 
 @bpf
-@section("sometag1")
+@section("tracepoint/syscalls/sys_enter_execve")
 def sometag(ctx: c_void_p) -> c_int64:
     return c_int64(1 - 1)
 

tests/passing_tests/var_rval.py

@@ -5,7 +5,7 @@
 
 
 @bpf
-@section("sometag1")
+@section("tracepoint/syscalls/sys_enter_execve")
 def sometag(ctx: c_void_p) -> c_int64:
     a = 1 - 1
     return c_int64(a)