Migrate PDE off the antiquated Equinox resolver and its API

[HannesWell]

As said in Bug 570198 and Bug 575374, "the org.eclipse.osgi.service.resolver [API] is antiquated and has not been used by the Equinox Framework since Kepler release." and PDE should be migrated to modern alternatives, ideally standard OSGi APIs.

This is intended as an umbrella issue to track all efforts in the area as well as to discuss the general approaches to solve this great effort.

The API in o.e.osgi.service.resolver is used for different areas within PDE.

• VersionRange: can be replaced with osgi.VersionRange (which it already extends). Used in PDE APIs so alternatives have to be added and existing methods have to be deprecated for removal.

• State: For the resolver State used in PDEState probably the OSGi resolver service and/or the implementations in the org.eclipse.osgi.container can serve as an replacement

• BundleDescription/Plugin dependencies: The initial proposal was to replace BundleDescription by BundleRevision. But in Support finding a model by Resource instead of BundleDescription #1062 (comment) @laeubi suggested to use the even more generic osgi Resouce API instead, which would allow even lighter Bundle/Plug-in representations

  you don't need a resolved state with bundles to compute the required information, it is already there in the meta-data, currently this requires PDE to download all bundles of a target platform even if only a few are used to resolve the projects classpath. Also this currently hinders PDE from using more than one target platform, e.g. you must always have one big-fat target that can satisfy all your workspace bundles, using different sets of bundles in the same workspace is not possible often without much efforts.

  And in combination with the suggested usage of the ResolveContext.getWirings() most of the information from the BundleRevision are also available for a osgi Resource , just in a slightly more abstract form. I agree, that it is probably possible to use mostly the Resources API.
  But maybe a migration is easier in two phases, first from BundleDescription to BundleRevision and the to Resource. The second step is then probably simpler, since a BundleRevision is already a Resource.

  As listed in Bug 570198, BundleDescription is used in several PDE APIs that need replacements and then have to be deprecated for removal.

For repeating patterns and required conveniences we can create a PDE internal utility class to use the Resources/Wiring API as convenient as the Equinox resolver API was.

[HannesWell]

• VersionRange: can be replaced with osgi.VersionRange (which it already extends). Used in PDE APIs so alternatives have to be added and existing methods have to be deprecated for removal.

With #1163 being submitted we reached the first milestone and have deprecated and provided replacements for all APIs using the Equinox resolver's VersionRange.
There are three other references to the Resolver's VersionRange left in the code. They are easy to replace but the surrounding code should be generally be revisited any ways.