Optimization to reduce MarkdownRenderer.render API calls

[tu2-atmanand]

• Optimization to reduce render API calls.
  This rendering functionality needs optimization, as I am calling the render API of Obsidian separately for task.Title and all individual task.subtask. These are too many API calls if there are many task Items.
  Since the body is separately rendered and its a hidden component. Atleast all the sub tasks can be combined together and render them together along with their checkboxes (this will restrict make it difficult to have the multiple checkbox dropdown feature i want to implement in future).
  Also later on, the task.title can be combined along with the subTasks and can be rendered all together. I can leave the main checkbox, since its in different section on left, rest the task.title and all the subtasks section falls under kind of like same section on right inside the task item card.

Originally posted by @tu2-atmanand in #37