[gen] Add VMSA PTE attribute annotations

[ShaleXIONG]

The supported attribute annotations are:

• PteWB
• PteWT
• PteNC
• PteGRE
• PtenGRE
• PtenGnRE
• PtenGnRnE
  For example diyone7 -metadata false -arch AArch64 -variant kvm PodWW PteNC L Rfe PodRR Fre generates:

AArch64 MP+popptenc.l+po
Variant=vmsa
{
 [x]=1;
 [y]=5;
 [PTE(y)]=(oa:PA(y), attrs:(Normal,ISH,iNC,oNC));
 0:X1=x; 0:X3=y;
 1:X1=x; 1:X3=y;
}
 P0           | P1          ;
 MOV W0,#2    | LDR W0,[X3] ;
 STR W0,[X1]  | LDR W2,[X1] ;
 MOV W2,#6    |             ;
 STLR W2,[X3] |             ;

exists (1:X0=6 /\ 1:X2=1)

The implementation separates existing implementations of (1) PTE field updates and (2) memory attributes separate and introduce new (3) PTE attributes. This new structure allows combination of (2) and (3).

Last, the new vmsa.t test file adds focused one-location diyone7 coverage for:

• standalone PTE annotations, such as PteV1 and PteHA
• standalone PTE memory attributes, such as PteWT
• combined PTE fields such as PteV1 PteWT
• attributes combined with fields, HA/HD, and access annotations such as Pte PteWT A