feat: make studio UI aware of override

[jansenk]

TL;DR - Make ORA studio UI aware of flexible course-wide override

JIRA: https://2u-internal.atlassian.net/browse/AU-1322

What changed?

• Add override to studio context
• If it's enabled, disable the select box for flexbile grading
• If it's enabled, show a message that the setting is enabled.

Developer Checklist

• Reviewed the release process
• Translations and JS/SASS compiled
• Bumped version number in openassessment/__init__.py and package.json

Testing Instructions

• Navigate to an ORA with a peer step in a course with the override turned off. The flexible setting should be active and there should be no message about the override.
• Turn the override on
• The input in the ORA settings should now be disabled and there should be a warning message.

Reviewer Checklist

Collectively, these should be completed by reviewers of this PR:

• I've done a visual code review
• I've tested the new functionality

FYI: @openedx/content-aurora

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (f9355d1) 94.99% compared to head (c34365f) 94.99%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1989   +/-   ##
=======================================
  Coverage   94.99%   94.99%           
=======================================
  Files         155      155           
  Lines       17107    17108    +1     
  Branches     1616     1616           
=======================================
+ Hits        16250    16251    +1     
  Misses        642      642           
  Partials      215      215           

Flag	Coverage Δ
unittests	94.99% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
openassessment/__init__.py	100.00% <100.00%> (ø)
openassessment/xblock/studio_mixin.py	93.22% <100.00%> (+0.03%)	⬆️

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[leangseu-edx]

LGTM 👍