Improve overload resolution and macro handling in Chain::Call

[apiology]

Fixes macro-based return type inference when the macro's $1/$2 placeholders reference the call's actual arguments, not just literal text elsewhere:

class Foo
  # @!macro
  #   @return [$1]
  def self.bar; end
end
Foo.bar(String)
#        ^^^^^^ should substitute into the return type

	Before	After
Foo.bar(String) inferred type	nil	String

Root cause: macro/directive reprocessing only ran when normal overload matching produced no type at all. bar's macro-based signature did produce a (wrong) type through the plain matching path, so reprocessing never ran. Chain::Call#inferred_pins's per-overload matching logic is extracted into match_overload_type, restructured so macro reprocessing runs whenever the matched type doesn't actually resolve the macro's placeholders against the real arguments.

Also adds spec coverage for related overload/macro edge cases; 8 of the new specs are pending, linked to tracking issues rather than left silently broken (#1223, #1246).

Testing: bundle exec rspec spec/source/chain/call_spec.rb spec/source_map/clip_spec.rb — 203 examples, 0 failures, 31 pending.

[apiology]

Resubmitting this against castwide/solargraph upstream.