properly fix #10053 ; FieldDefect msg now shows discriminant value + lineinfo, in all backends (c,vm,js) (#11955)

* fix #10053 FieldError for vm

* fixup

* FieldError now also shows runtime value of discriminant

* fix field error reporting in vm

* also report culprit line info in err msg

* fix errors for newruntime 2

* fix for js

* fixup

* PRTEMP4

* works

* works

* works perfect

* refactor

* std/private/repr_impl

* suppport --gc:arc

* cleanup

* refactor

* simplify

* simplify

* simplify

* fixup

* move out compiler.vmgen.genCustom

* fixup

* fixup

* add tests

* revert compiler/debugutils.nim

* simplify reprDiscriminant

* fixup

* lib/std/private/repr_impl.nim -> lib/system/repr_impl.nim

* try to fix D20210812T165220

* honor --declaredlocs

* control toFileLineCol via --declaredlocs

compiler/renderer.nim

@@ -1758,15 +1758,3 @@ proc getTokSym*(r: TSrcGen): PSym =
     result = r.tokens[r.idx-1].sym
   else:
     result = nil
-
-proc quoteExpr*(a: string): string {.inline.} =
-  ## can be used for quoting expressions in error msgs.
-  "'" & a & "'"
-
-proc genFieldDefect*(field: PSym, disc: PSym): string =
-  ## this needs to be in a module accessible by jsgen, ccgexprs, and vm to
-  ## provide this error msg FieldDefect; msgs would be better but it does not
-  ## import ast
-  result = field.name.s.quoteExpr & " is not accessible using discriminant " &
-    disc.name.s.quoteExpr & " of type " &
-    disc.owner.name.s.quoteExpr