docs, logging: required endpoints should documented, logs should make them obvious

# Problem

- If a request fails because it is blocked by the network, our logs don't always show the actual URL that failed.
- We don't have clear documentation about which endpoints are required for AWS Toolkit and Amazon Q to work.

see also: https://www.github.com/aws/aws-toolkit-vscode/issues/5753#issuecomment-2472184399

# Solution

1. Ensure that log messages mention the URL that failed.
2. ✅ Document required endpoints. Partial list (requires investigation):
- `https://idetoolkits.amazonwebservices.com` https://github.com/aws/aws-toolkit-vscode/blob/4235561f6a9e724f204ff5c6f66b8e98060a4e42/packages/core/src/shared/constants.ts#L12
- Other:
```
https://codewhisperer.us-east-1.amazonaws.com/
https://aws-toolkit-language-servers.amazonaws.com/
https://q.us-east-1.amazonaws.com
https://client-telemetry.us-east-1.amazonaws.com
https://cognito-identity.us-east-1.amazonaws.com
https://oidc.us-east-1.amazonaws.com
```
- Amazon Q endpoints: https://docs.aws.amazon.com/general/latest/gr/amazonq.html
- IdC endpoints: https://docs.aws.amazon.com/singlesignon/latest/userguide/get-set-up-for-idc.html
- https://docs.aws.amazon.com/amazonq/latest/qdeveloper-ug/vpc-interface-endpoints.html
- `com.amazonaws..q`
- `com.amazonaws..codewhisperer`

Start with packages/core/src/shared/constants.ts and the endpoint references in the issue, then trace the logging paths for network-blocked requests. Done means failure logs identify the URL that failed and documentation lists the required AWS Toolkit and Amazon Q endpoints, including the relevant regional endpoints.

Written by the indexing model from the issue text.