We were inspecting all trees on the classpath for every project, which
was not efficient and lead to duplicate results. This commit changes the
implementation so that the language server inspects only the source
trees of every project.

Some checks were redundant with the checks that are performed in
`namedTrees`, and can be removed. Also, exclude primary constructors in
`symbol`.

We never want to match them, so it's easier to exclude them here rather
than always add a check in the predicate function.

This include flag means that local symbols and trees should be
inspected.