assistant: Add Bedrock support (#21092)

Closes #16544

Release Notes:

- Added support for AWS Bedrock to the Assistant.

---------

Co-authored-by: Marshall Bowers <git@maxdeviant.com>
Co-authored-by: Anthony <anthony@zed.dev>
Co-authored-by: Anthony Eid <hello@anthonyeid.me>

crates/language_models/src/provider.rs

@@ -1,4 +1,5 @@
 pub mod anthropic;
+pub mod bedrock;
 pub mod cloud;
 pub mod copilot_chat;
 pub mod deepseek;