feat(instrumentation-express): add support for Express v5, take 2

This PR starts with @timfish's #2437 (Tim did all the hard work) and
makes it a smaller patch -- mostly by avoiding having separate
test/v4 and test/v5 trees.

Now that we are on JS SDK v2 and hence only support Node.js v18 as
a minimum (the same as express@5) the testing story is now simpler:
no need to avoid running some tests with older Node.js versions.
(See #2722 for a general discussion of the pain when having to do that.)

Obsoletes: #2437
Closes: #2435

Author: trentm