Process Tree allows regular SchedFork,Exec,Exit events to be disabled

[rafaeldtinoco]

Description

Discussion at: #3364 (comment)

// Initialize events state with mandatory events

	t.eventsState[events.SchedProcessExec] = events.EventState{}
	t.eventsState[events.SchedProcessExit] = events.EventState{}
	t.eventsState[events.SchedProcessFork] = events.EventState{}

There is no need for these events to always be enabled now IF capture isn't enabled.

Observations:

1. The SchedProcessExec is needed by processEvent (processSchedProcessExec) for the MntNs bucket and "Capture Exec" feature.
2. The SchedProcessFork is needed by processEvent (processSchedProcessFork) for converting start_time to Epoch time.
3. The Exit is only needed because of ebpf maps clean up.

Need to check if refactoring this is something needed/wanted.

[rafaeldtinoco]

Being worked at #2586