fixes #22939; fixes #16890; push should but doesn't apply to importc … (#22944)

…var/let symbols

fixes #22939
fixes #16890

Besides, it was applied to let/const/var with pragmas, now it is
universally applied.

```nim
{.push exportc.}
proc foo =
  let bar = 12
  echo bar
{.pop.}
```

For example, the `bar` variable will be affected by `exportc`.

(cherry picked from commit cecaf9c56b)

tests/stdlib/tsugar.nim

@@ -11,6 +11,23 @@ type # for capture test, ref #20679
   FooCapture = ref object
     x: int
 
+proc mainProc() =
+  block: # bug #16967
+    var s = newSeq[proc (): int](5)
+    {.push exportc.}
+    proc bar() =
+      for i in 0 ..< s.len:
+        let foo = i + 1
+        capture foo:
+          s[i] = proc(): int = foo
+    {.pop.}
+
+    bar()
+
+    for i, p in s.pairs:
+      let foo = i + 1
+      doAssert p() == foo
+
 template main() =
   block: # `=>`
     block:
@@ -85,22 +102,6 @@ template main() =
             closure2 = () => (i, j)
     doAssert closure2() == (5, 3)
 
-    block: # bug #16967
-      var s = newSeq[proc (): int](5)
-      {.push exportc.}
-      proc bar() =
-        for i in 0 ..< s.len:
-          let foo = i + 1
-          capture foo:
-            s[i] = proc(): int = foo
-      {.pop.}
-
-      bar()
-
-      for i, p in s.pairs:
-        let foo = i + 1
-        doAssert p() == foo
-
     block: # issue #20679
       # this should compile. Previously was broken as `var int` is an `nnkHiddenDeref`
       # which was not handled correctly
@@ -270,17 +271,16 @@ template main() =
         discard collect(newSeq, for i in 1..3: i)
       foo()
 
-proc mainProc() =
   block: # dump
     # symbols in templates are gensym'd
     let
-      x = 10
-      y = 20
+      x {.inject.} = 10
+      y {.inject.} = 20
     dump(x + y) # x + y = 30
 
   block: # dumpToString
     template square(x): untyped = x * x
-    let x = 10
+    let x {.inject.} = 10
     doAssert dumpToString(square(x)) == "square(x): x * x = 100"
     let s = dumpToString(doAssert 1+1 == 2)
     doAssert "failedAssertImpl" in s