Remove xblock-utils dependency

[Agrendalath]

Parent ticket: openedx/axim-engineering#915

This repository is using the xblock-utils package, which has been deprecated and migrated to within the xblock package.

In this ticket, we will:

• Make sure the repository is using xblock version 1.8.1 or above. Upgrade the version if required, preferably via the make upgrade command.
• Remove the xblock-utils package.
• Find and replace all the xblockutils.* imports with xblock.utils.*. Provide the fallback mentioned below.
• Make sure all the test cases are passing.
• Test the XBlock.

Example fallback for imports:

try:
    from xblock.utils.resources import ResourceLoader
    from xblock.utils.settings import ThemableXBlockMixin, XBlockWithSettingsMixin
except ModuleNotFoundError:  # For backward compatibility with releases older than Quince.
    from xblockutils.resources import ResourceLoader
    from xblockutils.settings import ThemableXBlockMixin, XBlockWithSettingsMixin

[kdmccormick]

Additional tasks discovered in #127, which I had to abandon over time constraints:

• Delete integration tests
• Remove Makefile entries, etc. regarding integration tests
• Remove bok-choy, selenium, and (maybe?) xblock-sdk from dev requirements
• Add XBlock[django] as a base requirement
• Recompile requirement .txt files

[kdmccormick]

@Agrendalath I noticed that 1.14.0 will fix the log warnings--thanks! When the upgrade lands in edx-platform master, assuming it's not risky, would you mind backporting it to Redwood? I think this would be a nice touch to make the release easier for operators to work with.

[Agrendalath]

@kdmccormick, do you mean backporting the version bump to Redwood? Because this XBlock is compatible with all releases back to at least Palm.

[kdmccormick]

@kdmccormick, do you mean backporting the version bump to Redwood?

Yes