[EnvVar]Treat well-known debugging environment variables as lists (#34689)

* [EnvVar] Treat well-known debugging environment variables as lists

The following environment variables are semi-colon lists, like "PATH"

* _NT_SYMBOL_PATH
* _NT_ALT_SYMBOL_PATH
* _NT_SYMCACHE_PATH

Treat them as lists in the Environment Variable editor.

Windows Debugger paths are [documented as being semi-colon
delimited][0]. The [`_NT_SYMCACHE_PATH` is used by WPA][1], and it also
documented as being semi-colon delimited.

[0]: https://learn.microsoft.com/en-us/windows/win32/debug/symbol-paths
[1]: https://learn.microsoft.com/en-us/windows-hardware/test/wpt/loading-symbols

* [EnvVar] Add SYMCACHE to expected words list

.github/actions/spell-check/expect.txt

@@ -1565,6 +1565,7 @@ SWC
 SWFO
 SWP
 SWRESTORE
+SYMCACHE
 SYMED
 SYMOPT
 SYNCMFT

src/modules/EnvironmentVariables/EnvironmentVariablesUILib/Models/Variable.cs

@@ -64,7 +64,15 @@ namespace EnvironmentVariablesUILib.Models
 
         private bool IsList()
         {
-            List<string> listVariables = new() { "PATH", "PATHEXT", "PSMODULEPATH" };
+            List<string> listVariables = new()
+            {
+                "_NT_ALT_SYMBOL_PATH",
+                "_NT_SYMBOL_PATH",
+                "_NT_SYMCACHE_PATH",
+                "PATH",
+                "PATHEXT",
+                "PSMODULEPATH",
+            };
 
             foreach (var name in listVariables)
             {