Instead of own complete product definitions just use the existing
o.e.platform.ide product and install all additionally required IUs while
tycho-surefire assembles the test-runtime.

In an earlier state the test-runtime was just provisioned from the
'o.e.sdk.ide' product, which had the drawback, that it included the
o.e.pde feature from the latest I-build and not the one just built in
the Maven reactor.
Instead of the 'o.e.sdk.ide' product, now 'o.e.platform.ide' is used
as base product. The latter doesn't contain the o.e.pde feature, which
allows us to install it from the reactor when tycho-surefire assembles
the test-runtime.

Follow-up on
- https://github.com/eclipse-pde/eclipse.pde/pull/1149