Bug 1724948 [wpt PR 29970] - Change `Tests.prototype.all_done` to require either...

Bug 1724948 [wpt PR 29970] - Change `Tests.prototype.all_done` to require either tests or pending remotes, a=testonly

Automatic update from web-platform-tests
Change `Tests.prototype.all_done` to require either tests or pending remotes

`Tests.prototype.all_done` used to treat the presence of at least one
test as a necessary condition for all tests to be done. This would be
false in cases where an exception is thrown inside the `setup` function,
but the code path that runs in that case doesn't use the `all_done()`
function.

However, if an exception is thrown inside the `setup` function in a
worker test, `tests.all_done()` is called in that code path, which
results in the completion message from the worker being ignored. This
change fixes this by changing the condition to require the presence of
either tests or remote contexts.

Closes #29777.

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wpt-commits: c563d3aaf49ab4f40eb16b4e99be9230e536286f
wpt-pr: 29970