Slow function (block_grade_me_tree)

[Fragonite]

While profiling a course, I observed that block_grade_me_tree is adding approximately 10 seconds to the page load time when logged in as a site admin. Student accounts are not as affected.

This issue can be addressed by taking the following steps:

• Minimise the number of database calls by batching them where possible.
• Move get_string calls outside of loops where possible.
• Update HTML generation (not necessarily a performance issue but it could definitely be improved).