Ensure that the CvtVectorToMask node is inserted in the right place

[tannergooding]

This fixes

[MethodImpl(MethodImplOptions.NoInlining)]
public static Vector<byte> M3(SveMaskPattern pattern)
{
    return Sve.CreateTrueMaskByte(pattern);
}

Which now correctly generates

; Method Program:M3(ubyte):System.Numerics.Vector`1[ubyte] (FullOpts)
G_M15394_IG01:  ;; offset=0x0000
            stp     fp, lr, [sp, #-0x10]!
            mov     fp, sp
						;; size=8 bbWeight=1 PerfScore 1.50

G_M15394_IG02:  ;; offset=0x0008
            uxtb    w0, w0
            movz    x1, #0x6E98      // code for System.Runtime.Intrinsics.Arm.Sve:CreateTrueMaskByte(ubyte):System.Numerics.Vector`1[ubyte]
            movk    x1, #0xE7A8 LSL #16
            movk    x1, #0x7FFC LSL #32
            ldr     x1, [x1]
            blr     x1
            ptrue   p7.b
            cmpne   p0.b, p7/z, z0.b, #0
            mov     z0.b, p0/z, #1
						;; size=36 bbWeight=1 PerfScore 13.00

G_M15394_IG03:  ;; offset=0x002C
            ldp     fp, lr, [sp], #0x10
            ret     lr
						;; size=8 bbWeight=1 PerfScore 2.00
; Total bytes of code: 52

Which is to say the IR:

N005 (  6,  7) [000003] --C--------                         *  RETURN    simd16 $VN.Void
N004 (  5,  6) [000002] --C--------                         \--*  HWINTRINSIC simd16 ubyte ConvertMaskToVector $200
N003 (  4,  5) [000001] --C--------                            \--*  HWINTRINSIC mask   ubyte CreateTrueMaskByte $140
N002 (  3,  4) [000004] -----------                               \--*  CAST      int <- ubyte <- int $100
N001 (  2,  2) [000000] -----------                                  \--*  LCL_VAR   int    V00 arg0         u:1 (last use) $80

rationalizes into:

               [000005] -----------                            IL_OFFSET void   INLRT @ 0x000[E-]
N001 (  2,  2) [000000] -----------                    t0 =    LCL_VAR   int    V00 arg0         u:1 (last use) $80
                                                            /--*  t0     int    
N002 (  3,  4) [000004] -----------                    t4 = *  CAST      int <- ubyte <- int $100
                                                            /--*  t4     int    arg0 in x0
N003 ( 17,  7) [000006] --C-G------                    t6 = *  CALL      simd16 System.Runtime.Intrinsics.Arm.Sve:CreateTrueMaskByte(ubyte):System.Numerics.Vector`1[ubyte]
N004 (  1,  1) [000007] -----------                    t7 =    HWINTRINSIC mask   ubyte CreateTrueMaskAll
                                                            /--*  t7     mask   
                                                            +--*  t6     simd16 
N005 ( 19,  9) [000008] --C-G------                    t8 = *  HWINTRINSIC mask   ubyte ConvertVectorToMask
                                                            /--*  t8     mask   
N004 (  5,  6) [000002] --C-G------                    t2 = *  HWINTRINSIC simd16 ubyte ConvertMaskToVector $200
                                                            /--*  t2     simd16 
N005 (  6,  7) [000003] --C-G------                         *  RETURN    simd16 $VN.Void

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[kunalspathak]

LGTM. Thanks!