[#12588] Part of Improve test code coverage of core components

[Surge747]

100% coverage on RichTextEditorComponent
and improves coverage on SessionsTable

Part of #12588

Outline of Solution

SessionTables improved coverage (PublishStatusTooltipPipe and SessionsTableComponent) (70.3% -> 100%)
Adds test cases for unexpected input (e.g., invalid and undefined statuses).
Improves test readability by using clear and meaningful variable names.
Reduces redundant setup code with a beforeEach block.
Ensures the code is more robust and resilient to edge cases, improving maintainability and reliability.

RichTextEditorComponent improved coverage (30%->100%)
The tests now verify all possible input properties (isDisabled, hasCharacterLimit, minHeightInPx, placeholderText, and richText) and ensure that custom values are correctly applied.
Added tests to simulate character count updates, keypress prevention, and content truncation for paste events.
Used a mock TinyMCE editor to closely mimic real editor behavior.
A MockRange class was introduced to accurately simulate Range objects, ensuring realistic cursor manipulation tests.
The setup function of TinyMCE was invoked manually, allowing detailed verification of event listeners (GetContent, keypress, paste).
Test functions were refactored with clearer naming conventions and logically grouped by feature (e.g., "Input Properties," "Output Events," "Character Limit Functionality").
setTimeout and done callbacks were used to ensure asynchronous actions (like setTimeout) are fully tested.

[github-actions]

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