VSCode becomes unusable with a large .aws/config file

## Problem
When using a large .aws/config file, the toolkit extensions slows down the whole IDE, making e.g. file creation incredibly slow

## Steps to reproduce the issue
1. Create a large .aws/config file (mine has 5k distinct profiles in it), I recommend using a seperate config file
2. start vscode with `AWS_CONFIG_FILE=/path/to/.aws/config-file code`
3. Try creating a new file in the IDE.

You can also open the developers tools console and see this message repeated (with different sizes):
```
WARN [mainThreadStorage] large extension state detected (extensionId: amazonwebservices.aws-toolkit-vscode, global: true): 820.7822265625kb. Consider to use 'storageUri' or 'globalStorageUri' to store this data on disk instead.
```

## Expected behavior
Everything works as with a small config file, especially when not using the connected features of the toolkit

## System details (run `AWS: About` and/or `Amazon Q: About`)

- OS: Darwin arm64 25.1.0
- Visual Studio Code extension host: 1.107.0
- AWS Toolkit: 3.90.0
- node: 22.21.1
- electron: 39.2.3

Reproduce the slowdown in VSCode with a large AWS config file and inspect the Developer Tools console for repeated mainThreadStorage warnings. Trace the toolkit behavior responsible for the oversized extension state; done means large configurations no longer make basic IDE actions unusable and the warning is resolved.

Written by the indexing model from the issue text.