Stop looking up the methods at compile time. For much speed.

[oxinabox]

#27
There is 1 key internal change of this, that should be invisible to users, more or less.
Rather than create a Method using @which, to decide if a method should be instrumented or not.
we instead query the function + argument against the set of rules.
Which is much faster, expectially in the case where no, or few @no_debug rules are set.
(as in the benchmark below).

However, there is 1 problem with this.
If you set_nodebug on a method, that takes fairly abstract arguments.
Then it will actually result in all more specific methods also being blocked.
I don't think that that is actually a serious usability issue.
As set_nodebug is mostly used ona function or module level.

• One possible resolution is to just ban set_nodebug from working on a method level.
• Another is to set make it legal but print a warning explaining its behavour.

A less problematic side effect of this change is that now setting no debug on a Module,
now takes out methods that belong to that module's functions,
even when those methods are defined in other modules.
I do not think this change is a problem, as I think that is the more reasonable behavour to have.
It is about knocking out a whole namepace, not knocking out a particular package.

using the "standard" summer test
for benchmarking debuggers:
(I have a feeling I am not using it the same way as in JuliaDebug/JuliaInterpreter.jl#204 (comment) though)

With this PR:

julia> @btime @iron_debug summer($(ones(40)))
  4.238 ms (16043 allocations: 626.09 KiB)
40.0

julia> @btime @iron_debug summer_inlined($(ones(40)))
  2.312 ms (7956 allocations: 284.27 KiB)
40.0

Current master:

julia> @btime @iron_debug summer($(ones(40)))
  9.792 ms (28160 allocations: 1.29 MiB)
40.0

julia> @btime @iron_debug summer_inlined($(ones(40)))
  3.545 ms (13097 allocations: 641.72 KiB)
40.0

[oxinabox]

Ok, I went with disabling setting of nodebug on methods.
Not really a useful feature anyway.

Assuming CI passes, then I will probably merge this tomorrow.