Revert "feat: allow users to set array length via args in @mtkmodel"

[YingboMa]

Reverts #3055

The above PR broke the following example.

julia> using ModelingToolkit

julia> @mtkmodel Fixed begin
           @parameters begin
               (r[1:2] = [0, 0]), [description = "Fixed absolute xy-position, resolved in planarWorld frame"]
               phi = 0, [description = "Fixed angle"]
           end

           @components begin
               frame_b = Frame()
           end

           @equations begin
               frame_b.x ~ r[1]
               frame_b.y ~ r[2]
               frame_b.phi ~ phi
           end
       end
ERROR: LoadError: KeyError: key :parameters not found
Stacktrace:
 [1] getindex
   @ ./dict.jl:498 [inlined]
 [2] parse_variable_def!(dict::Dict{…}, mod::Module, arg::Expr, varclass::Symbol, kwargs::OrderedCollections.OrderedSet{…}, where_types::Vector{…}; def::Nothing, indices::Nothing, type::Type, meta::Dict{…})
   @ ModelingToolkit ~/src/julia/ModelingToolkit/src/systems/model_parsing.jl:329
 [3] parse_variable_def!
   @ ~/src/julia/ModelingToolkit/src/systems/model_parsing.jl:193 [inlined]
 [4] parse_variable_arg(dict::Dict{…}, mod::Module, arg::Expr, varclass::Symbol, kwargs::OrderedCollections.OrderedSet{…}, where_types::Vector{…})
   @ ModelingToolkit ~/src/julia/ModelingToolkit/src/systems/model_parsing.jl:751
 [5] parse_variable_arg!(exprs::Vector{…}, vs::Vector{…}, dict::Dict{…}, mod::Module, arg::Expr, varclass::Symbol, kwargs::OrderedCollections.OrderedSet{…}, where_types::Vector{…})
   @ ModelingToolkit ~/src/julia/ModelingToolkit/src/systems/model_parsing.jl:716
 [6] parse_variables!(exprs::Vector{…}, vs::Vector{…}, dict::Dict{…}, mod::Module, body::Expr, varclass::Symbol, kwargs::OrderedCollections.OrderedSet{…}, where_types::Vector{…})
   @ ModelingToolkit ~/src/julia/ModelingToolkit/src/systems/model_parsing.jl:902
 [7] parse_model!(exprs::Vector{…}, comps::Vector{…}, ext::Base.RefValue{…}, eqs::Vector{…}, icon::Base.RefValue{…}, vs::Vector{…}, ps::Vector{…}, sps::Vector{…}, c_evts::Vector{…}, d_evts::Vector{…}, dict::Dict{…}, mod::Module, arg::Expr, kwargs::OrderedCollections.OrderedSet{…}, where_types::Vector{…})
   @ ModelingToolkit ~/src/julia/ModelingToolkit/src/systems/model_parsing.jl:505
 [8] _model_macro(mod::Module, name::Symbol, expr::Expr, isconnector::Bool)
   @ ModelingToolkit ~/src/julia/ModelingToolkit/src/systems/model_parsing.jl:71
 [9] var"@mtkmodel"(__source__::LineNumberNode, __module__::Module, name::Symbol, body::Any)
   @ ModelingToolkit ~/src/julia/ModelingToolkit/src/systems/model_parsing.jl:33
in expression starting at REPL[2]:1
Some type information was truncated. Use `show(err)` to see complete types.

[ChrisRackauckas]

Forgot to add docs and tests