Missing coverage for tail-call optimization across realms

[jugglinmike]

@bakkot reported the coverage gap in gh-2978. That issue has more detail on the missing tests, including why we may prefer to wait for a normative change to ECMA262 before writing them.

[bakkot]

Note that https://github.com/tc39/ecma262/pull/2495 has the relevant normative change, and https://github.com/tc39/test262/pull/3181 has the corresponding test.