Rename UMaskExt to UMask2 for Core events

[edwarddavidbaker]

The goal of this issue is to document renaming the core event attribute UMaskExt to UMask2. The goal is to align with Unit Mask 2 as used in the Intel Software Developer's Manual. This change only applies to core event files.

Example event

perfmon/PTL/events/pantherlake_cougarcove_core.json

Lines 469 to 495 in e49581a

	{
	"EventCode": "0x11",
	"UMask": "0x20",
	"UMaskExt": "0x01",
	"EventName": "ITLB_MISSES.STLB_HIT",
	"BriefDescription": "Instruction fetch requests that miss the ITLB and hit the STLB.",
	"PublicDescription": "Counts instruction fetch requests that miss the ITLB (Instruction TLB) and hit the STLB (Second-level TLB).",
	"Counter": "0,1,2,3,4,5,6,7,8,9",
	"PEBScounters": "0,1,2,3,4,5,6,7,8,9",
	"SampleAfterValue": "100003",
	"MSRIndex": "0x00",
	"MSRValue": "0x00",
	"Precise": "0",
	"CollectPEBSRecord": "2",
	"TakenAlone": "0",
	"CounterMask": "0",
	"Invert": "0",
	"EdgeDetect": "0",
	"Data_LA": "0",
	"L1_Hit_Indication": "0",
	"Errata": "null",
	"Offcore": "0",
	"Deprecated": "0",
	"Equal": "0",
	"PDISTCounter": "NA",
	"Speculative": "1"
	},

In the above example UMaskExt will be renamed to UMask2 to align with the SDM. Intel SDM reference snippets.

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Reference Links

1. https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html
2. Intel® 64 and IA-32 Architectures Software Developer's Manual Combined Volumes: 1, 2A, 2B, 2C, 2D, 3A, 3B, 3C, 3D, and 4