skip unnecessary alias-check in collect(::AbstractArray) from copyto!

[thchr]

As discussed on Slack with @MasonProtter & @jakobnissen, collect currently does a usually cheap - but sometimes expensive - aliasing check (via unalias->mightalias->dataid -> objectid) before copying contents over; this check is unnecessary, however, since the source array is newly created and cannot possibly alias the input.
This PR fixes that by swapping from copyto! to copyto_unaliased! in the _collect_indices implementations where the swap is straightforward (e.g., it is not so straightforward for the fallback _collect_indices(indsA, A), so I skipped it there).

This improves the following example substantially:

struct GarbageVector{N} <: AbstractVector{Int}
    v :: Vector{Int}
    garbage :: NTuple{N, Int}
end
GarbageVector{N}(v::Vector{Int}) where N = GarbageVector{N}(v, ntuple(identity, Val(N)))
Base.getindex(gv::GarbageVector, i::Int) = gv.v[i]
Base.size(gv::GarbageVector) = size(gv.v)

using BenchmarkTools
v = rand(Int, 10)
gv = GarbageVector{100}(v)
@btime collect($v);  # 30 ns (v1.10.4)  -> 30 ns (PR)
@btime collect($gv); # 179 ns (v1.10.4) -> 30 ns (PR)

Relatedly, it seems the fact that mightalias is comparing immutable contents as well - and hence slowing down the unalias check for the above GarbageVector via a slow objectid on tuples - is suboptimal. I don't know how to fix that though, so I'd like to leave that outside this PR. (Probably related to #26237)

[thchr]

Bump.

[thchr]

Bump; I think this is not likely to be very controversial.