Deprecate separate lb, ub arguments to IntegralProblem

[lxvm]

Fixes SciML/Integrals.jl#198
Fixes SciML/Integrals.jl#208

Specifically, this pr deprecates the following method:

@deprecate IntegralProblem(f::AbstractIntegralFunction,
    lb::Union{Number,AbstractVector{<:Number}},
    ub::Union{Number,AbstractVector{<:Number}},
    p = NullParameters(); kwargs...) IntegralProblem(f, (lb, ub), p; kwargs...)

@ChrisRackauckas this pr could also be a good time to decide on the promotion behavior for the endpoints of the integration domain. I actually think promotion should be handled at solve time since it could interfere with AD, e.g. using ForwardDiff and differentiating just the upper limit of integration.

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

Add any other context about the problem here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (416ca0a) 30.42% compared to head (4ca3c23) 27.18%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #576      +/-   ##
==========================================
- Coverage   30.42%   27.18%   -3.24%     
==========================================
  Files          53       53              
  Lines        4030     4021       -9     
==========================================
- Hits         1226     1093     -133     
- Misses       2804     2928     +124     

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[ChrisRackauckas]

this pr could also be a good time to decide on the promotion behavior for the endpoints of the integration domain. I actually think promotion should be handled at solve time since it could interfere with AD, e.g. using ForwardDiff and differentiating just the upper limit of integration.

Yes that's how we do it with the other problem types so it makes sense to do the same thing on IntegralProblem.

[ChrisRackauckas]

I think this just needs to update the related tests and its good to go.