chore: make integration tests more robust

- add generic functions to check received events in different manners:
  - ExpectAllInOrder
  - ExpectAllEqualTo
  - ExpectAtLeastOneOfEach
- add exec.go with helpers to run cmds via fork/exec and fork/syscall
- add waitForTraceeOutputEvents function to wait for tracee output
  events until buffer fills with certain number of events or
  timeout occurs
- remove tester.sh concentrating all event filter tests in
  event_filters_test.go

.gitignore

@@ -25,4 +25,4 @@ compile_commands.json
 .vagrant
 
 # binaries and build files
-dist
+dist