[JIT] Added BEGIN and END anchors for disasm output

[TIHan]

This adds explicit BEGIN and END anchors so that FileCheck will only check the assembly body of the disasm output. Before, the anchors were ambiguous, so now it is explicit.

Example:

; Assembly listing for method BasicBenchmark.Program+BasicBenchmark:Virtual():this (FullOpts)
; Emitting BLENDED_CODE for X64 with AVX512 - Windows
; FullOpts code
; optimized code
; rsp based frame
; partially interruptible
; No PGO data
; Final local variable assignments
;
;* V00 this [V00 ] ( 0, 0 ) ref -> zero-ref this class-hnd single-def <BasicBenchmark.Program+BasicBenchmark>
; V01 loc0 [V01,T01] ( 2, 5 ) ref -> rbx class-hnd single-def <System.IDisposable>
; V02 loc1 [V02,T00] ( 4, 13 ) int -> rsi ; V03 OutArgs [V03 ] ( 1, 1 ) struct (32) [rsp+00H] do-not-enreg[XS] addr-exposed "OutgoingArgSpace"
;
; Lcl frame size = 40
; BEGIN METHOD BasicBenchmark.Program+BasicBenchmark:Virtual():this
G_M37645_IG01: ;; offset=0000H
push rsi
push rbx
sub rsp, 40
;; size=6 bbWeight=1 PerfScore 2.25
G_M37645_IG02: ;; offset=0006H
test byte ptr [(reloc 0x7fff5936ec45)], 1 ; global ptr
je SHORT G_M37645_IG06
;; size=9 bbWeight=1 PerfScore 4.00
G_M37645_IG03: ;; offset=000FH
mov rcx, 0x1CF26001DC0 ; data for BasicBenchmark.Program:X
mov rbx, gword ptr [rcx]
xor esi, esi
;; size=15 bbWeight=1 PerfScore 2.50
G_M37645_IG04: ;; offset=001EH
mov rcx, rbx
mov r11, 0x7FFF58990090 ; code for System.IDisposable:Dispose():this
call [r11]System.IDisposable:Dispose():this
inc esi
cmp esi, 0x5F5E100
jl SHORT G_M37645_IG04
;; size=26 bbWeight=4 PerfScore 20.00
G_M37645_IG05: ;; offset=0038H
add rsp, 40
pop rbx
pop rsi
ret ;; size=7 bbWeight=1 PerfScore 2.25
G_M37645_IG06: ;; offset=003FH
mov rcx, 0x7FFF5936EC10
mov edx, 5
call CORINFO_HELP_GETSHARED_NONGCSTATIC_BASE
jmp SHORT G_M37645_IG03
;; size=22 bbWeight=0 PerfScore 0.00
; END METHOD BasicBenchmark.Program+BasicBenchmark:Virtual():this
; Total bytes of code 85, prolog size 6, PerfScore 39.50, instruction count 22, allocated bytes for code 85 (MethodHash=a3536cf2) for method BasicBenchmark.Program+BasicBenchmark:Virtual():this (FullOpts)
; ============================================================

[ghost]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

Issue Details

---

This adds explicit BEGIN and END anchors so that FileCheck will only check the assembly body of the disasm output.

Example:

; Assembly listing for method BasicBenchmark.Program+BasicBenchmark:Virtual():this (FullOpts)
; Emitting BLENDED_CODE for X64 with AVX512 - Windows
; FullOpts code
; optimized code
; rsp based frame
; partially interruptible
; No PGO data
; Final local variable assignments
;
;* V00 this [V00 ] ( 0, 0 ) ref -> zero-ref this class-hnd single-def <BasicBenchmark.Program+BasicBenchmark>
; V01 loc0 [V01,T01] ( 2, 5 ) ref -> rbx class-hnd single-def <System.IDisposable>
; V02 loc1 [V02,T00] ( 4, 13 ) int -> rsi ; V03 OutArgs [V03 ] ( 1, 1 ) struct (32) [rsp+00H] do-not-enreg[XS] addr-exposed "OutgoingArgSpace"
;
; Lcl frame size = 40
; BEGIN METHOD ANCHOR BasicBenchmark.Program+BasicBenchmark:Virtual():this
G_M37645_IG01: ;; offset=0000H
push rsi
push rbx
sub rsp, 40
;; size=6 bbWeight=1 PerfScore 2.25
G_M37645_IG02: ;; offset=0006H
test byte ptr [(reloc 0x7fff5936ec45)], 1 ; global ptr
je SHORT G_M37645_IG06
;; size=9 bbWeight=1 PerfScore 4.00
G_M37645_IG03: ;; offset=000FH
mov rcx, 0x1CF26001DC0 ; data for BasicBenchmark.Program:X
mov rbx, gword ptr [rcx]
xor esi, esi
;; size=15 bbWeight=1 PerfScore 2.50
G_M37645_IG04: ;; offset=001EH
mov rcx, rbx
mov r11, 0x7FFF58990090 ; code for System.IDisposable:Dispose():this
call [r11]System.IDisposable:Dispose():this
inc esi
cmp esi, 0x5F5E100
jl SHORT G_M37645_IG04
;; size=26 bbWeight=4 PerfScore 20.00
G_M37645_IG05: ;; offset=0038H
add rsp, 40
pop rbx
pop rsi
ret ;; size=7 bbWeight=1 PerfScore 2.25
G_M37645_IG06: ;; offset=003FH
mov rcx, 0x7FFF5936EC10
mov edx, 5
call CORINFO_HELP_GETSHARED_NONGCSTATIC_BASE
jmp SHORT G_M37645_IG03
;; size=22 bbWeight=0 PerfScore 0.00
; END METHOD ANCHOR BasicBenchmark.Program+BasicBenchmark:Virtual():this
; Total bytes of code 85, prolog size 6, PerfScore 39.50, instruction count 22, allocated bytes for code 85 (MethodHash=a3536cf2) for method BasicBenchmark.Program+BasicBenchmark:Virtual():this (FullOpts)
; ============================================================

Author:	TIHan
Assignees:	TIHan
Labels:	area-CodeGen-coreclr
Milestone:	-

[TIHan]

@jit-contrib this is ready, pending CI.