🚀 Feature: Export all BDD functions for "require interface"

[ScottFreeCode]

From my research in #2997, the "require interface's" exports are still missing:

• specify (alias of it)
• xspecify (alias of xit)
• xdescribe (can use context.suite.skip on the TDD side of the ||)
• context (context.context in this code; alias of describe)
• xcontext (alias of xdescribe)

It appears that the BDD functions are exported using || to separate BDD and TDD functions they're taken from, basically preferring to take the BDD functions but exporting the TDD functions under BDD names as a fallback, if I've understood the code correctly.

So, each of these should take from the BDD function with the same name; the ones marked "alias of" another should take from the same TDD function as the ones they're aliases of.

These additions don't need tests added unless #2982 is resolved first; if #2982 is resolved first then the added functions should be added to the new/improved test that resolves #2982.