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/ui/src/components/icon.rs

@@ -125,6 +125,7 @@ impl IconSize {
 pub enum IconName {
     Ai,
     AiAnthropic,
+    AiBedrock,
     AiAnthropicHosted,
     AiDeepSeek,
     AiGoogle,