Refactor: Do not include Tiptap Editor class in Vue reactivity

What does this MR do?

This Merge Request contains a series of refactoring changes that have as end goal removing the Tiptap’s Editor class instance from the Vue’s component reactive state.

Why are we doing this?

The Vue documentation strongly recommends not including ES6 class instances or objects created with constructor functions in the Component‘s reactive state created using data(). However, Tiptap’s documentation adopts this anti-pattern to react to changes in the document and the document’s selection.

This refactoring implements a solution that allows us to react to changes in the Editor’s document without breaking Vue’s rules.

What exactly does this MR contain?

• Injecting the Tiptap Editor class instance to all toolbar controls instead of passing the instance as a property. We don’t need to declare properties because we are not relying on Vue reactivity anymore.
• Creates a editor_state_observer renderless component that interfaces with the Tiptap’s Editor class instance events to allow Vue components to update their state based on these events.
• Refactors toolbar controls to use the editor_state_observer renderless component.

Screenshots or Screencasts (strongly suggested)

This MR does not introduce user-facing changes.

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team