Base: append!, resize!: convert length to Int before passing it on (#57585)

Reduces the number of invalidations from 512 to 505 on running this
code:

```julia
struct I <: Integer end
Base.Int(::I) = 7
```

Author: nsajko

base/array.jl

@@ -1348,7 +1348,7 @@ function append! end
 
 function append!(a::Vector{T}, items::Union{AbstractVector{<:T},Tuple}) where T
     items isa Tuple && (items = map(x -> convert(T, x), items))
-    n = length(items)
+    n = Int(length(items))::Int
     _growend!(a, n)
     copyto!(a, length(a)-n+1, items, firstindex(items), n)
     return a
@@ -1472,7 +1472,8 @@ julia> a[1:6]
  1
 ```
 """
-function resize!(a::Vector, nl::Integer)
+function resize!(a::Vector, nl_::Integer)
+    nl = Int(nl_)::Int
     l = length(a)
     if nl > l
         _growend!(a, nl-l)