Desktop: Fixes #5708: Scroll positions are preserved (#5826)

Features:
- Scroll position is preserved when the editor layout changes.
- Scroll position is remembered when a note selection changes.

Modifications:
- The current Sync Scroll feature (in v2.6.2) is modified to use line-percent-based scroll positions.
- Scroll position translation functions, Viewer-to-Editor and Editor-to-Viewer, are separated into V2L / L2E and E2L / L2V respectively.
- The scrollmap is moved from gui/utils/SyncScrollMap.ts to note-viewer/scrollmap.js.
- IPC Protocol about the scrollmap becomes not necessary and is removed.
- Ignores non-user scroll events to avoid sync with incorrect scroll positions.
- When CodeMirror is not ready, setEditorPercentScroll() is waited.
- Fixes the bug: An incorrect scroll position is sometimes recorded.
- Since scroll positions become line-percent-based, the following incompatibilities of scroll positions are fixed:
  - Between Editor and Viewer.
  - Between Viewer Layout and Split Layout of Viewer
  - Between Editor Layout and Split Layout of Editor

packages/app-desktop/gui/NoteTextViewer.tsx

@@ -2,7 +2,6 @@ import PostMessageService, { MessageResponse, ResponderComponentType } from '@jo
 import * as React from 'react';
 const { connect } = require('react-redux');
 import { reg } from '@joplin/lib/registry';
-import { SyncScrollMap, SyncScrollMapper } from './utils/SyncScrollMap';
 
 interface Props {
 	onDomReady: Function;
@@ -168,17 +167,6 @@ class NoteTextViewerComponent extends React.Component<Props, any> {
 		}
 	}
 
-	private syncScrollMapper_ = new SyncScrollMapper;
-
-	refreshSyncScrollMap(forced: boolean) {
-		return this.syncScrollMapper_.refresh(forced);
-	}
-
-	getSyncScrollMap(): SyncScrollMap {
-		const doc = this.webviewRef_.current?.contentWindow?.document;
-		return this.syncScrollMapper_.get(doc);
-	}
-
 	// ----------------------------------------------------------------
 	// Wrap WebView functions (END)
 	// ----------------------------------------------------------------