Allow specifiying path to use for stdin error messages (#24595)

Implements #24569

Adds `--stdinfile` flag for specifying the file to use in place of
`stdinfile.nim` in error messages. Will enable easier integration of
tooling with nim check

(cherry picked from commit 0cba752c8a)

tests/tools/tloadstdin.nim

@@ -0,0 +1,16 @@
+discard """
+  action: "compile"
+  cmd: "cat $file | $nim check --stdinfile:$file -"
+  # Don't believe cat and pipes works on windows
+  disabled: "win"
+"""
+
+import std/[assertions, paths]
+
+# Test the nimscript config is loaded
+assert defined(nimscriptConfigLoaded)
+
+assert currentSourcePath() == $(getCurrentDir()/Path"tloadstdin.nim")
+
+{.warning: "Hello".}  #[tt.Warning
+         ^ Hello]#

tests/tools/tloadstdin.nims

@@ -0,0 +1 @@
+--d:nimscriptConfigLoaded