feat(vscode): support running on monorepos

[alestiago]

Problem

Currently, the extension detects a Dart Frog project by traversing the file system upwards until it finds a Dart Frog project. If no Dart Frog project is found the vast majority of UI elements provided by the Dart Frog extension are hidden to avoid unnecessarily polluting the user's workspace.

By design, we originally expected users to open a workspace at the root of the Dart Frog project. However, some users do not do so because their workspace is a monorepo with one or more Dart Frog project inside it. This not only hides the Dart Frog's extension UI for them but also running commands such as "Start Development Server" will report:

Failed to find a Dart Frog project within the current workspace.

Currently, the extension can run in a monorepo but this requires the user to have an active route file open.

Proposal

There are multiple solutions, but after discussing with a closed group of users the preferred solution was to:

1. Traverse the file system downwards to find Dart Frog projects after failing to traverse upwards.
2. If more than one Dart Frog project is found when traversing downwards, then upon starting a server allow the user to pick their preferred project every single time. If the user finds the prompt annoying, then they should open the preferred Dart Frog project from the root.

Requirements

• Allow running the extension on monorepos
• Show user's a quick-pick prompt when there is more than one Dart Frog project on the monorepo and they attempt to run a command that requires a Dart Frog project to be specified