Remove support for entity variables in filecheck.

Now that the parser doesn't renumber indices, there's no need for entity
variables like $v0.

cranelift/filetests/regalloc/coalesce.cton

@@ -23,8 +23,8 @@ ebb1(v10: i32):
 
 function %trivial(i32) -> i32 {
 ebb0(v0: i32):
-    ; check: $(cp1=$V) = copy $v0
-    ; nextln: brnz $v0, $ebb1($cp1)
+    ; check: $(cp1=$V) = copy v0
+    ; nextln: brnz v0, ebb1($cp1)
     brnz v0, ebb1(v0)
     ; not: copy
     v1 = iadd_imm v0, 7
@@ -39,8 +39,8 @@ ebb1(v10: i32):
 ; A value is used as an SSA argument twice in the same branch.
 function %dualuse(i32) -> i32 {
 ebb0(v0: i32):
-    ; check: $(cp1=$V) = copy $v0
-    ; nextln: brnz $v0, $ebb1($cp1, $v0)
+    ; check: $(cp1=$V) = copy v0
+    ; nextln: brnz v0, ebb1($cp1, v0)
     brnz v0, ebb1(v0, v0)
     v1 = iadd_imm v0, 7
     v2 = iadd_imm v1, 56
@@ -55,15 +55,15 @@ ebb1(v10: i32, v11: i32):
 ; The interference can be broken with a copy at either branch.
 function %interference(i32) -> i32 {
 ebb0(v0: i32):
-    ; check: $(cp0=$V) = copy $v0
+    ; check: $(cp0=$V) = copy v0
     ; not: copy
-    ; check: brnz $v0, ebb1($cp0)
+    ; check: brnz v0, ebb1($cp0)
     brnz v0, ebb1(v0)
     v1 = iadd_imm v0, 7
     ; v1 and v0 interfere here:
     v2 = iadd_imm v0, 8
     ; not: copy
-    ; check: jump $ebb1($v1)
+    ; check: jump ebb1(v1)
     jump ebb1(v1)
 
 ebb1(v10: i32):
@@ -81,13 +81,13 @@ ebb0(v0: i32):
 
 ebb1(v10: i32, v11: i32):
     ; v11 needs to be isolated because it interferes with v10.
-    ; check: $ebb1($v10: i32 [$LOC], $(nv11a=$V): i32 [$LOC])
-    ; check: $v11 = copy $nv11a
+    ; check: ebb1(v10: i32 [$LOC], $(nv11a=$V): i32 [$LOC])
+    ; check: v11 = copy $nv11a
     v12 = iadd v10, v11
     v13 = icmp ult v12, v0
-    ; check: $(nv11b=$V) = copy $v11
+    ; check: $(nv11b=$V) = copy v11
     ; not: copy
-    ; check: brnz $v13, $ebb1($nv11b, $v12)
+    ; check: brnz v13, ebb1($nv11b, v12)
     brnz v13, ebb1(v11, v12)
     return v12
 }