Fix MultipleProcessesReturned caused by parent PID reuse

[psrok1]

As said in #679 and #938 - PPIDs are not guaranteed to be real and can be reused. On the other hand, initial enumeration of processes is done in order of EPROCESS linked list, so new processes should be further in list than older ones.

It means that if we have situation like:

{"PID": 348, "PPID": 336, "name": "csrss.exe"}
...
{"PID": 336, "PPID": 1984, "name": "taskhost.exe"}
{"PID": 2044, "PPID": 336, "name": "some_child_of_taskhost.exe"}

taskhost is further on list, so PPID of csrss.exe is phantom (and should be treated as process without parent) and the real children of PPID 336 are placed further in list.

In this PR:

• I removed creation of Mocked processes as creating a mock reserves a PID that shouldn't be reserved at that single moment.
• I removed MissingParentProcessError because we shouldn't throw an exception in that case: even if something weird happened with parent, we still have valuable information for newly created process that can be tracked - there is no point to throw whole entry because of that.

closes #679, closes #938

[psrok1]

Yup, works much better