`/home` partition or LVM logvol will be dropped and ignored after `bootc install to-existing-root`

If the system has a dedicated `/home` partition or LVM logvol, this part of disk will be dropped/ignored after `bootc install to-existing-root`. This part of disk will not be used by bootc system.
For example:
This is the system df output before `bootc install to-existing-root`.
```
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 4.0M 0 4.0M 0% /dev
tmpfs tmpfs 251G 0 251G 0% /dev/shm
tmpfs tmpfs 101G 12M 101G 1% /run
efivarfs efivarfs 512K 6.7K 506K 2% /sys/firmware/efi/efivars
/dev/mapper/cs_ampere--mtjade--altramax--01-root xfs 70G 2.5G 68G 4% /
/dev/nvme0n1p2 xfs 960M 201M 760M 21% /boot
/dev/nvme0n1p1 vfat 599M 7.0M 592M 2% /boot/efi
/dev/mapper/cs_ampere--mtjade--altramax--01-home xfs 819G 5.8G 813G 1% /home
tmpfs tmpfs 51G 0 51G 0% /run/user/0
tmpfs tmpfs 51G 4.0K 51G 1% /run/user/1000
```
This is the system df output after `bootc install`. Almost 800G disk space will not be used.
```
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 4.0M 0 4.0M 0% /dev
tmpfs tmpfs 251G 0 251G 0% /dev/shm
tmpfs tmpfs 101G 12M 101G 1% /run
efivarfs efivarfs 512K 6.6K 506K 2% /sys/firmware/efi/efivars
/dev/mapper/cs_ampere--mtjade--altramax--01-root xfs 70G 5.4G 65G 8% /sysroot
overlay overlay 7.3M 7.3M 0 100% /
/dev/nvme0n1p2 xfs 960M 56M 905M 6% /boot
tmpfs tmpfs 251G 96K 251G 1% /tmp
tmpfs tmpfs 51G 0 51G 0% /run/user/1000
```
Disk partition info:
```
Disk /dev/nvme0n1: 894.25 GiB, 960197124096 bytes, 1875385008 sectors
Disk model: SAMSUNG MZ1LB960HAJQ-00007
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 6A257643-7710-49F0-A752-0FD78B25237E

Device Start End Sectors Size Type
/dev/nvme0n1p1 2048 1230847 1228800 600M EFI System
/dev/nvme0n1p2 1230848 3327999 2097152 1G Linux filesystem
/dev/nvme0n1p3 3328000 1875384319 1872056320 892.7G Linux LVM


Disk /dev/mapper/cs_ampere--mtjade--altramax--01-root: 70 GiB, 75161927680 bytes, 146800640 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/cs_ampere--mtjade--altramax--01-swap: 4 GiB, 4294967296 bytes, 8388608 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop0: 7.29 MiB, 7643136 bytes, 1866 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/zram0: 8 GiB, 8589934592 bytes, 2097152 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/mapper/cs_ampere--mtjade--altramax--01-home: 818.66 GiB, 879033843712 bytes, 1716862976 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
```

Start with the bootc install to-existing-root entry point and reproduce the issue using the supplied df and partition/LVM layouts. Trace how the existing /home partition or logvol is handled; done means that mounted storage remains available and its capacity is not ignored after installation.

Scritto dal modello di indicizzazione a partire dal testo della issue.