faster active patterns by allowing hints for type guessing

[thautwarm]

Before:

julia> @active GlobalRef(x) begin
           if x isa GlobalRef
               (x.mod, x.name)
           else
               nothing
           end
       end

After:

julia> @active GlobalRef(x)::GlobalRef begin
           if x isa GlobalRef
               (x.mod, x.name)
           else
               nothing
           end
       end

[thautwarm]

 xs = [ GlobalRef(Main, :x), :(a.b), :+, GlobalRef(MLStyle, Symbol("@", :match)) ]

julia>  f(x) = @match x begin
                  GlobalRef(_, x) => x
                  :($_.$x) => x
                  _ => nothing
              end

julia> @btime [f(x) for x in xs]

before:

julia> @btime [f(x) for x in xs]
  442.929 ns (5 allocations: 272 bytes)
4-element Vector{Union{Nothing, Symbol}}:
 :x
 :b
 nothing
 Symbol("@match")

after

julia> @btime [f(x) for x in xs]
  408.000 ns (5 allocations: 272 bytes)
4-element Vector{Union{Nothing, Symbol}}:
 :x
 :b
 nothing
 Symbol("@match")