Improvements to language client error handling

[noeldevelops]

Summary of Changes

• Re-enables the language server in extension activation
• Adds one more error handler to the language client setup to catch initialization errors
• Removes the diagnostics processing, which does not have an effect on the lag with diagnostics we're seeing
• Checks the server "is running" value instead of "needs start" when deciding whether to reinitialize

Any additional details or context that should be provided?

Pull request checklist

Please check if your PR fulfills the following (if applicable):

Tests

• Added new
• Updated existing
• Deleted existing

Other

• All new disposables (event listeners, views, channels, etc.) collected as for eventual cleanup?

• Does anything in this PR need to be mentioned in the user-facing CHANGELOG or README?
• Have you validated this change locally by packaging and installing the extension .vsix file?

  gulp clicktest