Tests with 4096-byte sector size confirm that it is
safe to use O_DIRECT with page_compressed tables.
That had been disabled on Linux, in an attempt to fix MDEV-21584
which had been filed for the O_DIRECT problems earlier.

The fil_node_t::block_size was being set mostly correctly until
commit 10dd290b (MDEV-17380)
introduced a regression in MariaDB Server 10.4.4.

fil_node_open_file(): Only avoid setting O_DIRECT on
ROW_FORMAT=COMPRESSED tables that use KEY_BLOCK_SIZE=1 or 2
(1024 or 2048 bytes).

fil_ibd_create(): Avoid setting O_DIRECT on ROW_FORMAT=COMPRESSED tables
that use KEY_BLOCK_SIZE=1 or 2 (1024 or 2048 bytes).

fil_node_t::find_metadata(): Require fstat() to be always invoked
outside Microsoft Windows, so that fil_node_t::block_size can be set.

fil_node_t::read_page0(): Rely on find_metadata() to assign block_size.

Thanks to Vladislav Vaintroub for testing this on Microsoft Windows
using an old-fashioned rotational hard disk with 4KiB sector size.

Reviewed by: Vladislav Vaintroub

This is a port of commit 00f620b2
and commit 6505662c from 10.2.