subcommand and /abort fixes

- use AbortController in /abort instead of execption
- allow quiet abort
- allow loud abort
- allow abort reason
- abort when aborted in subcommand
- break out of loops when aborted inside
- fix parsing of subcommands with multiple commands

public/scripts/slash-commands/SlashCommandClosure.js

@@ -161,6 +161,7 @@ export class SlashCommandClosure {
                 let args = {
                     _scope: this.scope,
                     _parserFlags: executor.parserFlags,
+                    _abortController: this.abortController,
                 };
                 let value;
                 // substitute named arguments
@@ -254,6 +255,7 @@ export class SlashCommandClosure {
         if (this.abortController?.signal?.aborted) {
             const result = new SlashCommandClosureResult();
             result.isAborted = true;
+            result.isQuietlyAborted = this.abortController.signal.isQuiet;
             result.abortReason = this.abortController.signal.reason.toString();
             return result;
         }