[MASSEMBLY-1031] Respect dependency mediation when resolving dependencySets

[sbrougher-cainc]

This PR resolves transitive dependencies from the full declared dependency graph and applies the scope filter only when resolving, instead of pre-filtering the declared dependencies by scope before collection. Pre-filtering hid declarations that win Maven's mediation. This includes nearer versions, or directly provided dependencies, when the relevant declared dependency appeared transitively. This is clearly visible in the old version of the now-corrected src/it/projects/dependency-sets/massembly-1008/verify.groovy file. Despite being declared as test scoped in the pom, guava and all of its children were pulled into the assembly.

Note: in the new version of the code, even though guava is also declared as a transitive dependency of guice, guava will not be present in the final version of the assembly because the declared scope of guava is test. This is consistent with the compile/runtime classpath resolved by maven-dependency-plugin and the maven-jar-plugin.

This fixes when provided dependencies are included when they also occur transitively (MASSEMBLY-1031) and the wrong version being assembled on a cross-scope version conflict (MASSEMBLY-1026). The existing massembly-1008 integration test asserted the previous, incorrect output and is corrected to match Maven's resolution. Note: while this corrects two issues, this is because those two issues have the same underlying cause.

The substantive changes are just a few lines in DefaultDependencyResolver.java; everything else is testing.

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