Upgrade Underscore.string

[andy-armstrong]

FEDX-117

This is a second attempt to upgrade Underscore.string after this PR had to be reverted (https://github.com/edx/edx-platform/pull/11631). The hope is that the change in approach to deploying npm libraries (https://github.com/edx/edx-platform/pull/11938) will mean that there won't be strange failures in the bundled version.

Sandbox

• Build a sandbox for your branch and add a link here
  underscorestring.sandbox.edx.org

Testing

• i18n
• RTL
• Data is properly encoded in HTML templates to avoid XSS
• Unit, integration, acceptance tests as appropriate
• Analytics
• Performance
• Database migrations are backwards-compatible

Reviewers

If you've been tagged for review, please check your corresponding box once you've given the 👍.

• Code review: @andy-armstrong
• Code review: @AlasdairSwan

Post-review

• Squash commits

[andy-armstrong]

@bjacobel You'll need this PR's version of the UI Toolkit for some of my changes here to work:

openedx/edx-ui-toolkit#46

[andy-armstrong]

@bjacobel Another way to remove usages of Underscore.string is to replace calls to _.sprintf with StringUtils.interpolate. There are 53 such usages so that may be too much for one pull request, but most of them are in Underscore templates which are very self contained and easily tested.

[andy-armstrong]

There are also three usages of _.trim which are entirely in test files. These can just be changed to use the native string's trim method, since it works in all our supported browsers.

[bjacobel]

Sandbox coming online at underscorestring.sandbox.edx.org.

[bjacobel]

jenkins run bokchoy

[bjacobel]

jenkins run bokchoy

[bjacobel]

@andy-armstrong Tests now passing, would be worth doing a run through of manual tests on sandbox as well though I think. I edited your initial comment on this thread to include the pull request template.

cc @AlasdairSwan

[andy-armstrong]

👍 Looks great, @bjacobel.