Type-assert opts.delim_flags to reduce invalidations

[JamesWrigley]

In particular the last line of invalidations from PythonCall.jl (CC @cjdoris):

 inserting |(x::Number, y::PythonCall.Py) @ PythonCall.Core ~/git/PythonCall.jl/src/Core/Py.jl:432 invalidated:
   mt_backedges: 1: signature Tuple{typeof(|), Int64, Any} triggered MethodInstance for Base.JuliaSyntax._register_kinds!(::Dict{Int64, Union{Module, Symbol}}, ::Dict{UInt16, String}, ::Dict{String, UInt16}, ::Module, ::Int64, ::Vector{String}) (0 children)
                 2: signature Tuple{typeof(|), Int64, Any} triggered MethodInstance for Base.JuliaSyntax._register_kinds!(::Dict{Int64, Union{Module, Symbol}}, ::Dict{UInt16, String}, ::Dict{String, UInt16}, ::Module, ::Int64, ::Vector{String}) (0 children)
                 3: signature Tuple{typeof(|), Int64, Any} triggered MethodInstance for JuliaSyntax._register_kinds!(::Dict{Int64, Union{Module, Symbol}}, ::Dict{UInt16, String}, ::Dict{String, UInt16}, ::Module, ::Int64, ::Vector{String}) (0 children)
                 4: signature Tuple{typeof(|), Bool, Any} triggered MethodInstance for <=(::Any, ::Char) (0 children)
                 5: signature Tuple{typeof(|), Bool, Any} triggered MethodInstance for <=(::Char, ::Any) (9 children)
                 6: signature Tuple{typeof(|), UInt16, Any} triggered MethodInstance for Base.JuliaSyntax.parse_function_signature(::Base.JuliaSyntax.ParseState, ::Bool) (1155 children)

The issue is that ops.delim_flags was getting inferred to Any:

2220                 ambiguous_parens::Bool = opts::NamedTuple.maybe_grouping_parens::Any &&                                                                                                                                                   
2221                                    (peek_behind(ps::JuliaSyntax.ParseState)::@NamedTuple{kind::JuliaSyntax.Kind, flags::UInt16, orig_kind::JuliaSyntax.Kind, is_leaf::Bool}.kind::JuliaSyntax.Kind in KSet"macrocall $")::Bool            
2222                 emit(ps::JuliaSyntax.ParseState, mark::JuliaSyntax.ParseStreamPosition, K"tuple", (PARENS_FLAG::Core.Const(0x0100)|opts::NamedTuple.delim_flags::Any)::Any)                                                               
2223                 if ambiguous_parens::Bool                                                                                                                                                                                                 

But from reading parse_brackets() I think it's safe to restrict it to a RawFlags

[KristofferC]

Fixing #600 should fix this too.

[JamesWrigley]

Looks like the invalidations are also triggered by InitialValues.jl (in the dependency tree of OhMyThreads.jl):

 inserting |(x, ::Union{InitialValues.NonspecificInitialValue, InitialValues.SpecificInitialValue{typeof(|)}}) @ InitialValues ~/.julia/packages/InitialValues/OWP8V/src/InitialValues.jl:161 invalidated:
   mt_backedges: 1: signature Tuple{typeof(|), Int64, Any} triggered MethodInstance for Base.JuliaSyntax._register_kinds!(::Dict{Int64, Union{Module, Symbol}}, ::Dict{UInt16, String}, ::Dict{String, UInt16}, ::Module, ::Int64, ::Vector{String}) (0 children)
                 2: signature Tuple{typeof(|), Int64, Any} triggered MethodInstance for Base.JuliaSyntax._register_kinds!(::Dict{Int64, Union{Module, Symbol}}, ::Dict{UInt16, String}, ::Dict{String, UInt16}, ::Module, ::Int64, ::Vector{String}) (0 children)
                 3: signature Tuple{typeof(|), Bool, Any} triggered MethodInstance for <=(::Char, ::Any) (0 children)
                 4: signature Tuple{typeof(|), Bool, Any} triggered MethodInstance for <=(::Any, ::Char) (0 children)
                 5: signature Tuple{typeof(|), Missing, Any} triggered MethodInstance for <=(::Any, ::Char) (1 children)
                 6: signature Tuple{typeof(|), Missing, Any} triggered MethodInstance for <=(::Char, ::Any) (10 children)
                 7: signature Tuple{typeof(|), UInt16, Any} triggered MethodInstance for Base.JuliaSyntax.parse_function_signature(::Base.JuliaSyntax.ParseState, ::Bool) (1161 children)