fat: record time of file modification

* Add a function that updates the last-modified time of a fat
vnode; call it when the driver writes, creates, deletes,
or moves a file.
* The function optionally copies the new time from the vnode to the
corresponding direntry (useful if the calling function is not
going to do that anyway).
* Add a function that updates the last-modified time of the parent
directory of a fat vnode and copies the new time to the corresponding
direntry; call it when the driver deletes a file (not needed
for creating or moving because the parent directory vnodes are
directly accessible).
* Fixes #11119.

Change-Id: Ic7c0bda55190f236e9fd31d5d140d753138f7997
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5798
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

libroot: generate a name for nameless volumes

Generate a name indicating the volume size and filesystem.

Remove code that was doing that or similar things in various
filesystems.

Change-Id: I6b993735e58cdfaf1f19af575e918614c7fe5679
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5381
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Jessica Hamilton <jessica.l.hamilton@gmail.com>
Reviewed-by: John Scipione <jscipione@gmail.com>

FAT: More miscellaneous cleanup.

* Remove __RO__ hack inherited from BeOS sample code.
* Remove and excise unneeded macros.
* Remove readlink, VFS will return EINVAL in its absence anyway.

FAT: Make more use of C++ features and utility classes.

This driver was fully C until relatively recently, when it was
switched to C++ so that it could be used with fs_shell. However,
it still is mostly using C paradigms; so this commit begins the
refactor away from that.

If I did this correctly, there should not be any functional change.

Change-Id: Id87d17b2e019ccdd1c7f07156cfe2a2124496675
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4725
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

file_system/fat: Fix minor typo in last commit. Unintentional uchar to char

Change-Id: I51aab4690c6964c1daf1a2c8882756c393e354dd

file_system/fat: Rework driver for fs_shell support

* Introduce fat_shell for build system fat manipulation
* Will theoretically let us do away with mtools when we
have another internal tool for partition manipulation

Change-Id: I661be556e79009842f157a9402c8f85da85d6336
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3556
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>