[Question] Discover tests after delay or on-demand

### Environment
dotnet: 5.0.301
vscode: 1.59.1
extension: 0.7.5

### Question
When loading a project two things happen: 1) roslyn analyzers are run on all projects, and 2) tests are discovered - and this happens simultaneously. On a large workspace with multiple projects and thousands of tests, this is slooooooow.

Is it possible not to automatically discover tests (and do that on demand instead), or to delay by a few minutes? I looked for a setting that controls this but couldn't find one, maybe I'm not searching for the right words.

(I'm unsure whether this is possible via the extension, or is a vscode thing.)

Start by tracing the extension's project-loading, Roslyn analyzer, and test-discovery entry points to determine whether discovery is controlled by the extension or VS Code. Check existing settings and issue discussion for an on-demand or delayed mode; done would be a decided implementation scope or a documented configuration path.

Written by the indexing model from the issue text.