refactor(amazonq): improve error handling of workspace index

[leigaol]

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Description

Improve error handling of workspace index:

1. Log error when no file is found in the workspace for indexing.
2. Do not send LSP messages if the language server has not started.

These 2 are not customer facing changes.

Checklist

• My code follows the code style of this project
• I have added tests to cover my changes
• A short description of the change has been added to the CHANGELOG if the change is customer-facing in the IDE.
• I have added metrics for my changes (if required)

License

I confirm that my contribution is made under the terms of the Apache 2.0 license.

[leigaol]

I am fixing unit tests

[Will-ShaoHua]

@leigaol let's not merge it until release is done