Rename intenral code to 'FindUsages' so it better reflects that it can present results for more than just FindReferences.

Move Remote features down to lower levels now that the RemoteHostClient is available from the Workspace layer.

- Fixes #496, an error when finding reference on namespaces defined in
metadata
- Groups all namespace definitions & references under a single node,
which itself is non-navigable. Prior to this change, there would be lots
of top-level nodes for the same namespace with 0 references.

Now that the comment formatting issue is fixed in the Formatter type, we can run the formatter on the remainder of the VB code base.

closes #1424

These tests were broken in #1396, and this is a test-only fix.

Fixes internal issue #1138943.

In the SymbolFinder API, references to constructors are included as references to both the constructor method symbol and the related type symbol. Because reference locations are deduplicated across all results shown in Find References, we have to decide which definition node to use as the parent. Prior to this change the first related definition returned to us by the SymbolFinder won, but this ordering was not guaranteed to be consistent. This change introduces a precedence ordering for definitions returned by the SymbolFinder that currently guarantees that members will be preferred over types.

Additionally, this change removes the requirement that definitions shown in Find References have distinct locations. This allows us to meaningfully separate references between a type and its default constructor which has the same location.