Snippets: Move snippets into the core of editor (#13937)

Release Notes:

- Move snippet support into core editor experience, marking the official
extension as deprecated. Snippets now show up in any buffer (including
plain text buffers).

crates/snippet_provider/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "snippet_provider"
+version = "0.1.0"
+edition = "2021"
+publish = false
+license = "GPL-3.0-or-later"
+
+[lints]
+workspace = true
+
+[dependencies]
+anyhow.workspace = true
+collections.workspace = true
+fs.workspace = true
+futures.workspace = true
+gpui.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+snippet.workspace = true
+util.workspace = true