Implement LCA host/host addons logic in ember-cli

[brendenpalmer]

This PR implements host addons/LCA host logic in ember-cli and updates addon bundling caching to use these host addons, rather than only considered bundled addons by the project.

An LCA host in this context is defined as the lowest common ancestor that is considered a host amongst all bundle hosts (engines/project) by the same name in the project.

The behavior in ember-cli needs to differ than the original implementation in ember-engines because we need to know this information up-front during addon instantiation, rather than after all addons in the project have been instantiated. As a result, the method for determining the LCA host/host addons is different: because we don't have access to addon instances, we use PackageInfo objects to compute this information. It's worth noting that PackageInfo objects do not have knowledge of their parents, so we do a breadth-first traversal, keeping track of all paths until we discover the intended engine (represented by a PackageInfo).

For example, given the following project addon structure:

        --Project--
         /      \
        /        \
   Lazy Engine A  \
                Addon A
                  |
                  |
             Lazy Engine B
              /          \
             /            \
        Lazy Engine A   Lazy Engine C

• The LCA host for Lazy Engine A is the project
• The LCA host for Lazy Engine B is the project
• The LCA host for Lazy Engine C is Lazy Engine B

Similarly, we're also interested in all of the host package infos for a given LCA host; in the above example: hostAndAncestorBundledPackageInfos for each are considered to be:

• hostAndAncestorBundledPackageInfos for lazy engine A includes all non-lazy dependencies of its LCA host & above (in this case, just the project)
• hostAndAncestorBundledPackageInfos for lazy engine B includes all non-lazy dependencies of its LCA host & above (in this case, just the project)
• hostAndAncestorBundledPackageInfos for lazy engine C includes non-lazy deps of lazy engine B & non-lazy deps of the project (LCA host & above)

As part of this, we also expose a getLCAHost method so that ember-engines can prefer to use this method if it exists; we prefer that the computation for all of this has a single source of truth for both ember-engines and bundle addon caching.

[davecombs]

Some minor changes to ask for more descriptive member names and some more documentation of methods, but otherwise this looks good! Nice work.

[davecombs]

Found a few more cases that look like something is missing.