Adds ability to install a missing bsc version

[TwitchBronBron]

Adds the ability to install brighterscript versions automatically without requiring it to exist in ${workspaceFolder}/node_modules.

1. After this PR, the bsdk value can support the following values:

   • an absolute path to a preinstalled version of brighterscript (i.e. C:/roku/brighterscript)
   • a relative path to a preinstalled version of brighterscript (i.e. ./node_modules/brighterscript)
   • an exact version of brighterscript from the npm registry (i.e. 0.67.6, 1.0.0-alpha.36)
   • an absolute path to a .tgz file (i.e. C:/downloads/brighterscript-0.67.6.tgz)
   • a relative path to a .tgz file (i.e. ./packages/brighterscript-0.67.6.tgz)
   • a URL to a .tar file (i.e. npm install https://github.com/rokucommunity/brighterscript/releases/download/v0.67.6/brighterscript-0.67.6.tgzz)

2. We've added a new setting called npmCacheRetentionDays which determines how long to wait before deleting unused brighterscript versions from the local cache.

3. Added a new command called clearNpmPackageCache which will clear all downloaded brighterscript packages

4. Added a new series of menu options for downloading brighterscript versions, and also a few maintenance items like opening the install directory or clearing the downloaded files
   

Here's a demo of the feature in action:

bsc-picker.mp4

TODO:

• add menu item/command to clear all cached versions
• delete bsc versions that are older than 45 days (make this configurable)
• add vscode.window.onDidChangeWindowState event to mark a bsc version's "last used date"
• show all npm versions in the dropdown
• show mainline and prerelease versions in separate menus
• verify the extension storage gets cleaned up on extension uninstall (there's no way to do this, it's probably fine?)

[TwitchBronBron]

@chrisdp what do you think about this command name and the message?

[TwitchBronBron]

@chrisdp what do you think of this message?

[rokucommunity-bot]

Hey there! I just built a new version of the vscode extension based on 112a5d1. You can downloaded the .vsix here and then follow these installation instructions.

[rokucommunity-bot]

Hey there! I just built a new version of the vscode extension based on 43e015f. You can downloaded the .vsix here and then follow these installation instructions.