Documentation: ext4: Move inode table short docs into its own file

Documentation: ext4: Move inode table short docs into its own file

The short description of inode table is in bitmaps.rst alongside the
proper bitmpas documentation. The docs file is short enough that it fits
whole browser screen on desktop, which implies that when readers click
"Inode Table", they will essentially see bitmaps docs.

Move inode table short description.

Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Acked-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250620105643.25141-7-bagasdotme@gmail.com