`install to-disk` should create bigger ESP (likely 2G) for composefs+UKI installations by default

Currently, `bootc install to-disk` will create a 1GB ESP, which is likely too small for most use case with a UKI.

As data points, Atomic Desktops UKIs are ~250MB, so 3 UKIs (during updates) will be 75% full and with bootloaders, firmware updates and potentially other firmware files in there, it would be already full and we would have no room for the future. 2GB should give us some room.

For the Atomic Desktops, this will likely be configured in Anaconda but it should probably be configurable in bootc as it heavily depends on what you put in the initrd.