move widestrs out of system (#20462)

* move widestrs out of system

* fix osproc

tests/stdlib/t15663.nim

@@ -3,5 +3,7 @@ discard """
   output: "Test"
 """
 
+import std/widestrs
+
 let ws = newWideCString("Test")
-echo ws
+echo ws

tests/stdlib/tenvvars.nim

@@ -49,6 +49,7 @@ template main =
 main()
 
 when defined(windows):
+  import std/widestrs
   proc c_wgetenv(env: WideCString): WideCString {.importc: "_wgetenv", header: "<stdlib.h>".}
 proc c_getenv(env: cstring): cstring {.importc: "getenv", header: "<stdlib.h>".}
 

tests/stdlib/tosenv.nim

@@ -50,6 +50,7 @@ static: main()
 main()
 
 when defined(windows):
+  import std/widestrs
   proc c_wgetenv(env: WideCString): WideCString {.importc: "_wgetenv", header: "<stdlib.h>".}
 proc c_getenv(env: cstring): cstring {.importc: "getenv", header: "<stdlib.h>".}
 

tests/stdlib/twchartoutf8.nim

@@ -10,6 +10,7 @@ import std/[syncio, assertions]
 when not defined(windows):
   echo "OK"
 else:
+  import std/widestrs
   {.push gcsafe.}
 
   const CP_UTF8 = 65001'i32