additionalDisks: support for optional and customizable mount point

### Description

Currently, the additional disks are always mounted at `/mnt/lima-` and expected to be one of the support fileystem formats e.g. ext2-4, xfs

The current behaviour when the filesystem type specified is unsupported is that the disk is simply ignored by Lima during startup.

I would like to propose that we provide explicit option to disable mounting the disk, and an extra option to customize the mount point, which should give us a configuration option similar to the following.

```yaml
additionalDisks:
- name: string
format: bool
mount: bool # if the disk should be auto-mounted by Lima
mountPoint: string # custom mountPoint for the disk
fsType: string
```
**PS:** Colima relies on the current behaviour to prevent Lima from mounting a disk.