* TINY-10305: Empty unescaped Zwsp text nodes in TrimBody.trim and implement Zwsp-trimming in content APIs

* TINY-10305: Empty unescaped text containing zwnbsp in TrimBody.trim

* TINY-10305: Refactor TrimBody.trim

* TINY-10305: Add createTreeWalker filters to directly isolate nodes containing zwsp

- empty zwsp comments instead of removing them to minimise effects and be consistent with handling of unescaped zwsp text

* TINY-10305: Replace nodeValue = '' with nodeValue = null

* TINY-10305: Simplify emptyAllNodeValuesInWalker and improve tests in TrimBodyTest

* TINY-10305: Add tests for hasUnescapedZwspText and emptyUnescapedZwspTexts

* TINY-10305: Update UndoManagerTest, EditorGetContentRawTest, and LevelsTest due to changed comment exclusion behavior

* TINY-10305: Add unescaped zwsp text tests to UndoManagerTest

* TINY-10305: Add tests to EditorGetContentRawTest

* TINY-10305: Add tests to LevelsTest

* TINY-10305: Add tests to EditorResetContentTest

* TINY-10305: Add tests in AutoSavePluginTest

* TINY-10305: Implement user-input zwsp trimming in insertContent

* TINY-10305: Implement user-input zwsp trimming in setContent

* TINY-10305: Implemenet zwsp trimming for all branches of getContent

* TINY-10305: Add zwnbsp removal tests for Editor.save, Editor.resetContent, and content initialization

* TINY-10305: Add changelog entries

* TINY-10305: Convert unescapedTextParents to a map for faster lookup

* TINY-10305: Improve trim test in TrimBodyTest

* TINY-10305: Revert GetContentImpl changes

* TINY-10305: Replace editor.getBody().innerHTML assignments with TinyApis(editor).setContentRaw in tests

* TINY-10305: Revert InlineEditorSaveTest

* TINY-10305: Replace setContent with setRawContent in AutoSavePluginTest

* TINY-10305: Use setRawContent in tests where zwsp is part of content

* TINY-10305: Create InsertZwsp alien module for textpatterns

* TINY-10305: Update changelog entry wording

* TINY-10305: Rename keep_zwsp to preserve_zwsp

* TINY-10305: Update EditorContentTest to avoid Firefox-specific output

* TINY-10305: Create InsertZwspTest

* TINY-10305: Use Tools.makeMap to create unescapedTextParentsMap in TrimBody

* TINY-10305: Address Safari-specific output in content tests

* TINY-10305: Remove InsertZwsp alien module and add insert function in Zwsp module

* TINY-10305: Pass string to makeMap in TrimBody

* TINY-10305: Amend ZwspInsertTest label

* TINY-10319: Prepare for 6.7.3 Community Release