fixes to colonful reshape

[nsajko]

Fixes #54245

[nhz2]

LGTM

[nsajko]

ping

[nsajko]

ping

[jishnub]

The type assertions added here appear to have broken reshape using BigInts. Are these essential for type-inference?
E.g. the following works on Julia v1.10, but is broken on nightly:

julia> using FillArrays

julia> reshape(Fill(1, 2), big(2), :)
2×1 Fill{Int64}, with entries equal to 1

Edit: FillArrays appears to directly call this internal function, which it probably shouldn't. However, is reshape necessarily expected to convert indices to Int?

[nsajko]

_reshape_uncolon is only ever (legally) called from that one reshape method, which itself only accepts Union{Int,Colon} dims.

julia/base/reshapedarray.jl

Lines 129 to 130 in b0b7a85

	reshape(parent::AbstractArray, dims::Tuple{Vararg{Union{Int,Colon}}}) = reshape(parent, _reshape_uncolon(parent, dims))
	@inline function _reshape_uncolon(A, dims)