Make all file access 64-bit (uint64_t)

[akien-mga]

Forward port of #47254 to master. Draft for now as I haven't tested the changes yet, nor done a full pass to check potential type mismatches on calls to get_buffer() and similar.

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This changes the types of a big number of variables.

General rules:

• Using uint64_t in general. We also considered int64_t but eventually
  settled on keeping it unsigned, which is also closer to what one would expect
  with size_t/off_t.
• We only keep int64_t for seek_end (takes a negative offset from the end)
  and for the Variant bindings, since Variant::INT is int64_t. This means
  we only need to guard against passing negative values in core_bind.cpp.
• Using uint32_t integers for concepts not needing such a huge range, like
  pages, blocks, etc.

In addition:

• Improve usage of integer types in some related places; namely, DirAccess,
  core binds.

Note:

• On Windows, _ftelli64 reports invalid values when using 32-bit MinGW with
  version < 8.0. This was an upstream bug fixed in 8.0. It breaks support for
  big files on 32-bit Windows builds made with that toolchain. We might add a
  workaround.

Fixes #44363.
Fixes godotengine/godot-proposals#400.

[akien-mga]

I made a test build for Windows (32-bit and 64-bit, both editor and templates) to help validate this PR: https://downloads.tuxfamily.org/godotengine/testing/4.0-dev-pr48768-windows.zip

See #47254 (comment) for suggestions on how to make a reproduction project.

[akien-mga]

I made a test build for Windows (32-bit and 64-bit, both editor and templates) to help validate this PR: https://downloads.tuxfamily.org/godotengine/testing/4.0-dev-pr48768-windows.zip

Did some testing with this build like in #47254 (comment)

I have the same results, big PCKs are working properly, and this error also happens when trying to get too big a buffer:

ERROR: Condition "p_size < 0" is true. Returning: ERR_INVALID_PARAMETER
   at: resize (./core/templates/cowdata.h:260)
ERROR: Can't resize data to 2672612761 elements.
   at: (core/core_bind.cpp:1331)

That seems to be related to #46842.

Also tested the "Embed PCK" option with a Win32 binary exported from the Win32 editor and it works fine.

Edit: However I seem to get a different MD5 sum every time I export, so it seems there's something that makes the PCK non-deterministic in master.

[akien-mga]

Should be good to go as since it works in my tests (I just pushed an amend to handle a few missed get_len() and get_buffer() return types that could be uint64_t).