Can't use searchsorted with Date ranges on 32-bit

[simonbyrne]

julia> using Dates

julia> searchsorted(Date(2019,1,1):Month(2):Date(2020,1,1), Date(2019,3,2))
ERROR: MethodError: no method matching searchsorted(::StepRange{Date,Month}, ::Date, ::Int64, ::Int64, ::Base.Order.ForwardOrdering)
Closest candidates are:
  searchsorted(::AbstractArray{T,1} where T, ::Any, ::Int32, ::Int32, ::Base.Order.Ordering) at sort.jl:208
  searchsorted(::AbstractArray{T,1} where T, ::Any; lt, by, rev, order) at sort.jl:294
  searchsorted(::AbstractArray{T,1} where T, ::Any, ::Base.Order.Ordering) at sort.jl:292
Stacktrace:
 [1] searchsorted(::StepRange{Date,Month}, ::Date, ::Base.Order.ForwardOrdering) at ./sort.jl:292
 [2] #searchsorted#6(::Function, ::Function, ::Nothing, ::Base.Order.ForwardOrdering, ::Function, ::StepRange{Date,Month}, ::Date) at ./sort.jl:294
 [3] searchsorted(::StepRange{Date,Month}, ::Date) at ./sort.jl:294
 [4] top-level scope at none:0

The problem is that the searchsorted bisection expects Int, but length on date ranges returns an Int64.

[simonbyrne]

We really should have specialised methods for these in any case.

[kmsquire]

Ref: #20839, where length of date ranges was forced to Int64 (it was previously type unstable with type Union{Int32, Int64}).