Changing profile does not reload the S3 buckets

## Problem

When using multiple profiles in a .aws/config file, the explorer lets us dynamically switch from one profile to another.

The issue is that if the `S3` section was open with one profile in the explorer, it does not get refreshed when switching to a different profile. In order to refresh and see the buckets for the newly selected profile, one must **restart vscode** or at least restart the extensions server, which is less than ideal.

> [!NOTE]
> The refresh used to work just fine some months ago, so something got changed recently which broke this behavior.

## Steps to reproduce the issue

1. Setup multiple profiles in a `~/.aws/config` file
2. Select one profile in the explorer
3. Open the S3 section in the explorer, see the buckets associated with that profile
4. Select another profile
5. See that the S3 section does not get refreshed, and the buckets associated with the new profile are not accessible

## System details

- OS: MacOS
- Visual Studio Code version: 1.99.3
- AWS Toolkit version: 3.70.0

Start by tracing the S3 explorer's profile-switch handling in the VS Code extension and reproduce the issue with two profiles from ~/.aws/config. Verify that changing profiles refreshes the open S3 section and exposes the newly selected profile's buckets without restarting VS Code or the extensions server.

Written by the indexing model from the issue text.