Allow Int64 values within IO#read_at

[Blacksmoke16]

Fixes #10032.

The C bindings have this arg typed as SizeT, which from what I know is an unsigned int. Do we need to worry/do anything about the case where an Int64 is passed on a 32bit system where a sufficiently large enough Int64 would overflow a UInt32?

[Blacksmoke16]

  In src/file.cr:822:18
  
   822 | io = PReader.new(self, offset, bytesize)
                      ^--
  Error: no overload matches 'File::PReader.new' with types File, Int32, Int32

Oh, I would have thought they would have been upcasted...

[straight-shoota]

We'll' need overloads to accept at least Int32 for backwards compatibility. I suppose other types didn't work before.

[asterite]

Oh, I would have thought they would have been upcasted

Yeah, I would have liked that too...

#9618

[Blacksmoke16]

@straight-shoota Fixed in latest commit.

@asterite Yea that feature would have been perfect here. No reason not to do that that I can think of.

[bcardiff]

Checking, why is this PR a breacking-change?

[Sija]

@bcardiff it's no more after 37b486c