assistant_tools: Enable diff-fenced edit parser for all Gemini models (#32812)

I saw recently we added diff-fenced edit parser which improves the
overall edit performance of gemini models in this PR: #32737. The idea
is to enable it to all the models which has gemini as their id as this
will help copilot and openrouter provider as they seem to aggregate all
these models under one umbrella. I thought about adding a new method in
LanguageModel as vendor_name() which returns the underlying actual model
provider name but felt like a too early abstraction for a method to be
used at one place.

Release Notes:

- N/A

crates/assistant_tools/src/edit_agent/edit_parser.rs

@@ -75,7 +75,7 @@ impl FromStr for EditFormat {
 impl EditFormat {
     /// Return an optimal edit format for the language model
     pub fn from_model(model: Arc<dyn LanguageModel>) -> anyhow::Result<Self> {
-        if model.provider_id().0 == "google" {
+        if model.provider_id().0 == "google" || model.id().0.to_lowercase().contains("gemini") {
             Ok(EditFormat::DiffFenced)
         } else {
             Ok(EditFormat::XmlTags)