feat: autocomplete using inferred type instead of declared type in a function

[Octogonapus]

A function parameter's declared type is used to autocomplete that parameter throughout the function, even when a more precise inferred type is known. For example:

abstract type Parent end

struct Child1 <: Parent
    field1::Int
end

struct Child2 <: Parent
    field2::String
end

function foo(x::Parent)
    if x isa Child1
        # can't autocomplete x.field1
        x::Child1
        # still can't autocomplete x.field1
        x = x::Child1
        # still can't autocomplete x.field1, even though the language server knows x is of type Child1
        (x::Child1) # still can't autocomplete x.field1
    end
end

This issue is a feature request to use the inferred type for autocompletion, instead of always using the declared type from the function signature.