fix: AWS Bedrock inference profile ID conversion for region-specific endpoints (#3386)

Fixes #3370

AWS switched to requiring region-prefixed inference profile IDs instead
of foundation model IDs for on-demand throughput. This was causing
ValidationException errors.

Added auto-detection based on boto3 client region to convert model IDs
like meta.llama3-1-70b-instruct-v1:0 to
us.meta.llama3-1-70b-instruct-v1:0 depending on the detected region.

Also handles edge cases like ARNs, case insensitive regions, and None
regions.

Tested with this request.
```json
{
  "model_id": "meta.llama3-1-8b-instruct-v1:0",
  "messages": [
    {
      "role": "system",
      "content": "You are a helpful assistant."
    },
    {
      "role": "user",
      "content": "tell me a riddle"
    }
  ],
  "sampling_params": {
     "strategy": {
        "type": "top_p",
        "temperature": 0.7,
        "top_p": 0.9
      },
      "max_tokens": 512
  }
}
```
<img width="1488" height="878" alt="image"
src="https://github.com/user-attachments/assets/0d61beec-3869-4a31-8f37-9f554c280b88"
/>

tests/unit/providers/test_bedrock.py

@@ -0,0 +1,53 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from llama_stack.providers.remote.inference.bedrock.bedrock import (
+    _get_region_prefix,
+    _to_inference_profile_id,
+)
+
+
+def test_region_prefixes():
+    assert _get_region_prefix("us-east-1") == "us."
+    assert _get_region_prefix("eu-west-1") == "eu."
+    assert _get_region_prefix("ap-south-1") == "ap."
+    assert _get_region_prefix("ca-central-1") == "us."
+
+    # Test case insensitive
+    assert _get_region_prefix("US-EAST-1") == "us."
+    assert _get_region_prefix("EU-WEST-1") == "eu."
+    assert _get_region_prefix("Ap-South-1") == "ap."
+
+    # Test None region
+    assert _get_region_prefix(None) == "us."
+
+
+def test_model_id_conversion():
+    # Basic conversion
+    assert (
+        _to_inference_profile_id("meta.llama3-1-70b-instruct-v1:0", "us-east-1") == "us.meta.llama3-1-70b-instruct-v1:0"
+    )
+
+    # Already has prefix
+    assert (
+        _to_inference_profile_id("us.meta.llama3-1-70b-instruct-v1:0", "us-east-1")
+        == "us.meta.llama3-1-70b-instruct-v1:0"
+    )
+
+    # ARN should be returned unchanged
+    arn = "arn:aws:bedrock:us-east-1:123456789012:inference-profile/us.meta.llama3-1-70b-instruct-v1:0"
+    assert _to_inference_profile_id(arn, "us-east-1") == arn
+
+    # ARN should be returned unchanged even without region
+    assert _to_inference_profile_id(arn) == arn
+
+    # Optional region parameter defaults to us-east-1
+    assert _to_inference_profile_id("meta.llama3-1-70b-instruct-v1:0") == "us.meta.llama3-1-70b-instruct-v1:0"
+
+    # Different regions work with optional parameter
+    assert (
+        _to_inference_profile_id("meta.llama3-1-70b-instruct-v1:0", "eu-west-1") == "eu.meta.llama3-1-70b-instruct-v1:0"
+    )