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/project/Cargo.toml

@@ -63,6 +63,7 @@ shlex.workspace = true
 similar = "1.3"
 smol.workspace = true
 snippet.workspace = true
+snippet_provider.workspace = true
 terminal.workspace = true
 text.workspace = true
 util.workspace = true