add hash(Integer) fast-path

[oscardssmith]

Previously this used the hash(Real) path which is a bunch slower since the decomposition needs a lot more normalization and the conditions for when the fast-paths were applicable were more complicated.

# Before
@btime hash(x, UInt(1234)) setup=(x=Int128(rand(Int)))
 12.390 ns (0 allocations: 0 bytes)

julia> @btime hash(x, UInt(1234)) setup=(x=rand(Int128))
 23.768 ns (0 allocations: 0 bytes)

#After
julia> @btime hash(x, UInt(1234)) setup=(x=Int128(rand(Int)))
 5.039 ns (0 allocations: 0 bytes)

julia> @btime hash(x, UInt(1234)) setup=(x=rand(Int128))
 17.538 ns (0 allocations: 0 bytes)

[oscardssmith]

Closing since #49996 gets the same performance.