implements https://github.com/nim-lang/RFCs/issues/258 (#15503)

* implements https://github.com/nim-lang/RFCs/issues/258

* don't be too strict with custom pragma blocks

* cast pragmas: documentation

* added most missing inference query procs to effecttraits.nim

doc/manual.rst

@@ -6031,12 +6031,12 @@ so that it can be used for debugging routines marked as ``noSideEffect``.
 
 
 To override the compiler's side effect analysis a ``{.noSideEffect.}``
-pragma block can be used:
+``cast`` pragma block can be used:
 
 .. code-block:: nim
 
   func f() =
-    {.noSideEffect.}:
+    {.cast(noSideEffect).}:
       echo "test"
 
 
@@ -7501,7 +7501,7 @@ To disable the GC-safety checking the ``--threadAnalysis:off`` command line
 switch can be used. This is a temporary workaround to ease the porting effort
 from old code to the new threading model.
 
-To override the compiler's gcsafety analysis a ``{.gcsafe.}`` pragma block can
+To override the compiler's gcsafety analysis a ``{.cast(gcsafe).}`` pragma block can
 be used:
 
 .. code-block:: nim
@@ -7511,7 +7511,7 @@ be used:
     perThread {.threadvar.}: string
 
   proc setPerThread() =
-    {.gcsafe.}:
+    {.cast(gcsafe).}:
       deepCopy(perThread, someGlobal)