startup: extension fails if ~/.aws/config is missing

## Problem

I have

> Error running command aws.login: command 'aws.login' not found. This is likely caused by the extension that contributes aws.login.

after installing the AWS toolkit extension and clicking on "Connect to AWS"


## Steps to reproduce the issue

## Expected behavior

I should be able to connect to an IAM role after installing the extension.

## System details (run the `AWS: About Toolkit` command)

- OS: MacOS Ventura 13.5.2
- Visual Studio Code version: 1.82.2 (Universal)
- AWS Toolkit version: v1.90.0
- AWS CLI: installed at `/usr/local/bin/aws`: `aws-cli/2.3.5 Python/3.8.8 Darwin/22.6.0 exe/x86_64`

Reproduce the startup failure with ~/.aws/config absent, using the listed AWS Toolkit and VS Code versions if available. Trace the extension startup and “Connect to AWS” entry point to determine why aws.login is not registered; done means the command is available and connecting to an IAM role succeeds without that file.

Written by the indexing model from the issue text.