allow generic compileTime proc folding (#22022)

fixes #10753, fixes #22021, refs #19365 (was fixed by #22029, but more
faithful test added)

For whatever reason `compileTime` proc calls did not fold if the proc
was generic ([since this folding was
introduced](c25ffbf262 (diff-539da3a63df08fa987f1b0c67d26cdc690753843d110b6bf0805a685eeaffd40))).
I'm guessing the intention was for *unresolved* generic procs to not
fold, which is now the logic.

Non-magic `compileTime` procs also now don't fold at compile time in
`typeof` contexts to avoid possible runtime errors (only the important)
and prevent double/needless evaluation.

(cherry picked from commit f7c11a8978)

tests/vm/tgenericcompiletimeproc.nim

@@ -0,0 +1,29 @@
+block: # issue #10753
+  proc foo(x: int): int {.compileTime.} = x
+  const a = foo(123)
+  doAssert foo(123) == a
+
+  proc bar[T](x: T): T {.compileTime.} = x
+  const b = bar(123)
+  doAssert bar(123) == b
+  const c = bar("abc")
+  doAssert bar("abc") == c
+
+block: # issue #22021
+  proc foo(x: static int): int {.compileTime.} = x + 1
+  doAssert foo(123) == 124
+
+block: # issue #19365
+  proc f[T](x: static T): T {.compileTime.} = x + x
+  doAssert f(123) == 246
+  doAssert f(1.0) == 2.0
+
+block:
+  # don't fold compile time procs in typeof
+  proc fail[T](x: T): T {.compileTime.} =
+    doAssert false
+    x
+  doAssert typeof(fail(123)) is typeof(123)
+  proc p(x: int): int = x
+
+  type Foo = typeof(p(fail(123)))