feat: Extracting LTI XBlock from edx-platform

[ttqureshi]

Ticket
LTI Block Extraction from the edx-platform.

Test PR

Here's the Test PR for extracted LTIBlock

File References

• xblocks-contrib/lti/lti.py has been extracted from edx-platform/xmodule/lti_block.py
• xblocks-contrib/lti/lti_2_util.py has been extracted from edx-platform/xmodule/lti_2_util.py
• xblocks_contrib/lti/static/css/lti.css has been extracted from edx-platform/xmodule/static/css-builtin-blocks/LTIBlockDisplay.css
• xblocks_contrib/lti/static/js/src/lti.js has been extracted from edx-platform/xmodule/js/src/lti/lti.js
• xblocks_contrib/lti/templates/lti.html has been extracted from edx-platform/lms/templates/lti.html
• xblocks_contrib/lti/templates/lti_form.html has been extracted from edx-platform/lms/templates/lti_form.html

Acceptance Criteria

• Extracted XBlock user experience should behave normal if required global css variables donesn't exist
• Extracted XBlock funcationality should work fine after turning its relevant Django Settings Flag
• In existing built in xblock implementation of edx-platform, update the status or data of the XBlocks. Then change the Django Settings flag and verify after shifting to extracted one, XBlocks are maintaining their required states (including XBlock completion status).
• Also test the vice versa of above step, change XBlock from Extracted one to Built in implementation to check fallback case testings.
• i18n is supported in the XBlock
• Create a course, add multiple XBlocks in the course. Keep different XBlocks in diversity of states (done/un-done etc). Export the course then validate the XBlock states after importing it again.
• Make a test PR for the extracted Block in edx-platform like this and fix the test cases if required.
• Write further unit test cases for good code coverage

[ttqureshi]

Currently blocked on: openedx/XBlock#823

PR link: openedx/XBlock#830.

[ttqureshi]

This PR is up for review

cc: @farhan @salman2013 @irtazaakram

[kdmccormick]

LGTM.

Before merging can you update the xblocks-contrib README so that it says this block is "In Development" instead of "Placeholder"? Can you do the same for annotatable and word_cloud too? (we forgot to update the list for those)

[ttqureshi]

Before merging can you update the xblocks-contrib README so that it says this block is "In Development" instead of "Placeholder"? Can you do the same for annotatable and word_cloud too? (we forgot to update the list for those)

sure

[ttqureshi]

@kdmccormick I've made the requested changes, bumped the minor version and added the CHANGELOG entry.