Fix running Python commands that include paths with spaces (#21981)

This PR fixes running Python commands that include paths with spaces by
wrapping python commands and their arguments in quotation marks.

I fixed this only in Python as I noticed this while trying to run
`pytest` in Zed.

Probably this is not the best approach as it doesn't fix other languages
too, though I don't know enough about the codebase to fix it like that.
I'm not even sure if it's actually feasible right now.

I didn't add tests for this either as I couldn't really understand how
to easily to that, I tried to look at other languages but couldn't find
one that tests their `ContextProvider` directly.

Release Notes:

- Fix running Python commands that include paths with spaces

---------

Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>

crates/task/src/lib.rs

@@ -135,6 +135,10 @@ impl VariableName {
     pub fn template_value(&self) -> String {
         format!("${self}")
     }
+    /// Generates a `"$VARIABLE"`-like string, to be used instead of `Self::template_value` when expanded value could contain spaces or special characters.
+    pub fn template_value_with_whitespace(&self) -> String {
+        format!("\"${self}\"")
+    }
 }
 
 impl FromStr for VariableName {