Improve performance of isapprox(::AbstractArray, ::AbstractArray) when rtol = 0 (#47464)

Co-authored-by: Lilith Orion Hafner <[email protected]>

Author: thchr

stdlib/LinearAlgebra/src/generic.jl

@@ -1772,7 +1772,7 @@ function isapprox(x::AbstractArray, y::AbstractArray;
     nans::Bool=false, norm::Function=norm)
     d = norm(x - y)
     if isfinite(d)
-        return d <= max(atol, rtol*max(norm(x), norm(y)))
+        return iszero(rtol) ? d <= atol : d <= max(atol, rtol*max(norm(x), norm(y)))
     else
         # Fall back to a component-wise approximate comparison
         # (mapreduce instead of all for greater generality [#44893])