CompletionTriggerKind should distinguish between manually invoked and always on completion

As of LSP 3.16, CompletionTriggerKind takes the value Invoked for both manually invoked (for ex: ctrl + space in VSCode) completions and always on (what the spec refers to as 24/7 completions).

/**
 * Completion was triggered by typing an identifier (24x7 code
 * complete), manual invocation (e.g Ctrl+Space) or via API.
 */
export const Invoked: 1 = 1;

These should be distinguished since the completion results returned in certain scenarios should be different based on how the completions were triggered. For ex: gopls, the LSP implementation for Go supports completions for relevant identifiers in comments but these can be annoying if the user is using always on completion (since comments are mostly prose) but helpful when the user actually wants to trigger completions while typing identifiers in comments. See https://github.com/golang/go/issues/41596

Start by reading the CompletionTriggerKind definition shown in the issue and compare it with the LSP 3.16 behavior described there. Determine how manually invoked and always-on completion should be represented while preserving the existing protocol meaning; done means the distinction is specified clearly for implementations and clients.