Fix: Support empty Vector{Any} ([]) in system keyword arguments (fixes #4206)

[ommishra0719]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

I added a one-line dispatch to defsdict in src/systems/system.jl to handle Vector{Any}:
defsdict(d::Vector{Any}) = isempty(d) ? Dict{Any, Any}() : defsdict(Dict(d))

[hersle]

Would fix #4206.

[ommishra0719]

Do I need to make any other changes, since it didn't pass a few tests?

[AayushSabharwal]

Not necessarily. Some of these failures look spurious. I reran the necessary jobs to make sure.