Re: Available disk space per tablespace

V7 passes the tested Windows SQL and psql cases on native ARM64 and
emulated x64.

Both pg_tablespace_avail variants agree with independent
GetDiskFreeSpaceExW samples for pg_default, pg_global and a custom
path containing spaces. Before/after samples use a 64MB tolerance for
concurrent changes.

Default/custom access, CREATE grants, pg_read_all_stats membership and
missing name/OID diagnostics pass. Actual psql \db+ shows Free and No
Access as expected.

Full integration builds and setup groups pass; the checkout includes
earlier Windows changes. All tested paths share one NTFS volume.
Quotas, different volumes and older-server psql compatibility weren't
tested. The disposable clusters were stopped and custom tablespaces
dropped.

Happy to provide the script and samples.

Original discussion:
https://www.postgresql.org/message-id/CAF0whue1Vn-BiMRD3Kw0B5QQRgZXukXdCvkm8TmVycx5bj0WVA@mail.gmail.com

Best,

Harrison