[NTOS:KD64][NTOS:KDBG] Fix spinlocks use

[NTOS:KD64][NTOS:KDBG] Fix spinlocks use

Raise IRQL before entering debugger, so that KeAcquireSpinLockAtDpcLevel works as expected.
 - HIGH_LEVEL since we don't know where we are coming from.

Do not try to read debug symbol from files in KDBG.
 - There is no reason that this works if Mm didn't map it in the first place.