Created transition BackendTestUtils2

[gcatron]

Summary:
Created transition BackendTestUtils2 which is a copy of BackendTestUtils that has been ported to EE2. This is an intermediate step so tests can be ported one at a time. Once all users of BackendTestUtils have been ported BackendTestUtils2 will replace BackendTestUtils. Also ported HyphenTest which uses the new BackendUtils2.

Documentation: NA

Work on #3239

Test Plan: ninja check, verify HyphenTest passes.

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[jfix71]

@gcatron Ok I have a (hopefully not too annoying) request 😄. In theory this PR shouldn't be so hard to review because there probably aren't so many differences between BackendTestUtils2 and BackendTestUtils. But in practice because there's a single commit here with the new BackendTestUtils2 files and so it's hard to tell what's changed vs the original versions.

So, instead of directly copying + adding the new BackendTestUtils2 files, can you do something like:

git mv BackendTestUtils.cpp BackendTestUtils2.cpp
git commit BackendTestUtils.cpp -m "Just moved old version to new"
cp BackendTestUtils2.cpp BackendTestUtils.cpp
git add BackendTestUtils.cpp
git commit BackendTestUtils.cpp -m "Bring back the old version with the same name"
// Make changes to BackendTestUtils2.cpp
git commit BackendTestUtils2.cpp -m "New changes."

Then on GH it'd be possible to see the actual meaningful changes to BackendTestUtils2.cpp in the "New changes" commit.

I tried the above out myself on EE->EE3 and it's pretty easy and works great. See this branch and this commit. And it would make reviewing this PR and similar ones in the future much easier/more effective.

[gcatron]

Closing this PR, #3263 was created for the same changes but a series of stacked commits to make review easier.