devtools: Expose introductionType to devtools clients (#38541)

in the devtools protocol, [source
forms](https://firefox-source-docs.mozilla.org/devtools/backend/protocol.html#loading-script-sources)
announced in `resources-available-array` messages can include the
`introductionType`, which more or less mirrors the field of the same
name in SpiderMonkey’s CompileOptions.

this patch exposes `introductionType` accordingly, allowing us to check
for the correct values in automated tests.

Testing: new coverage in devtools tests
Fixes: part of #36027

---------

Signed-off-by: Delan Azabani <dazabani@igalia.com>
Co-authored-by: atbrakhi <atbrakhi@igalia.com>

components/devtools/lib.rs

@@ -552,6 +552,7 @@ impl DevtoolsInstance {
             source_info.url,
             source_content,
             source_info.content_type,
+            source_info.introduction_type,
         );
         let source_actor_name = source_actor.name.clone();
         let source_form = source_actor.source_form();