Expose Autocomplete on enableBasicAutocompletion

[mkslanc]

Issue #, if available: #5730

Description of changes:
This update enhances the editor's autocompletion API by exposing the editor.completer instance immediately after enableBasicAutocompletion is enabled. Previously, accessing autocomplete properties required triggering the completion popup, which limited early configuration and customization. Now, developers can immediately set up and adjust autocomplete behaviors as soon as autocompletion is activated.

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Pull Request Checklist:

• No backwards incompatible changes were made to Ace's public interface which is defined through the main typings file (ace.d.ts) and its references:
  • https://github.com/ajaxorg/ace/blob/master/ace.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-modes.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-extensions.d.ts