Code Review | Extracted Problem Block PR's

[farhan]

Do the code review of the extracted Problem Block PR's:

• PR #63: baseline copy from edx-platform + import updates
openedx/xblocks-contrib#63
• PR #151: critical fixes to pass Python and JavaScript tests (needs thorough review)
openedx/xblocks-contrib#151
• PR #153: code quality and docs only (split out to keep PR #151 smaller)
openedx/xblocks-contrib#153
edx-platform
• PR #37136: enables the extracted Problem Block and clears tests
#37136
Suggested review order: #63 → edx-platform #37136 → #153 → #151