[EGD-5757] Fix backup API

Fix backup endpoint to work with new paths and FS api
The flow is based on the design in confluence.

Merge branch 'EGD-5737-merge-master-to-exp-lbr-fix'

[EGD-5737] Fix filesystem unit tests

Remove old VFS and utils::filesystem calls
Update unittest lists

[EGD-5737] Fix ugly crash on boot

Fix ugly crash on boot fs

[EGD-5737] Merge master into experimental

Keep experimental up to date with changes from master

[EGD-5609] Fix lfs partition erase size bug

Storing LFS erase size in the boot byte is not possible
because Linux kernel is unable to detect the partitions
after change boot bytes to values other than 0x80 or 0x00

In this patch LFS_BLOCK_SIZE is moved to the second
MBR bootcode AREA

[EGD-4495] Check partitions during registering new disk image

Check partitions validity when registering disk.
Add unittest and test disk image generation.

[EGD-5522] Remount fs R/W for backup or update

After setting vFAT to be read only by default backup,
update and factory reset procedures need to remount R/W
first.

[EGD-4761] Add unit tests for littlefs and dual-mount

Additionally, old tests have been refactored for consistency
and readability. Also, files were added to littlefs test image.

[EGD-5515] Remove unused code lfxextension

Remove unused code for detecting block size from user blocks

[EGD-5072] Refactor legacy VFS functions

Functions were refactored and renamed for better readability.
Some of them were moved to different files. In stat_vfs function
the order of member initializations was corrected.

[EGD-5392] Add switch vfat to RO mode

VFAT partition should be mounted in RO mode by default
because writing to FAT filesystem is unsafe.
Writing is allowed only in the LFS filesystem.
If upgrade is needed FAT partition can be temporary
switched to RW mode using mount() syscall with REMOUNT flag
but it should be switched to RO mode again after upgrade.

[EGD-5146] Add read LFS block size from part

Add littlefs block size from partition bootable offset

[EGD-5350] Add increase lfs cluster size

Incrase LFS clustrer size and cache bitmap improve
the FS free blocks scan time, because LFS don't have
free block bitmap.

[EGD-5014] Change MMC erase logic

MMC erase group size is 512 kB which would enforce
512 kB blocks on file system. Since for our purposes this
would be inefficient erase command has been disallowed.

[EGD-5334] Fix phone crash when MTP access

Fix phone crash when accessing file when new filesystem is used

[EGD-5014] Fix global FS locks

Global locks are redundant and lower the performance.

[EGD-5014] Add eMMC block device API

Add PureOS wrapper for eMMC driver with support
for basic block device operations.

[EGD-5020] Add autodetect filesystem

Add support for autodetect filesystem in the fs core

[EGD-4498] Fix code after code review #1

Fixed some small minor issus in the RO mode in the vfs