[canary] TPM is always selected as default

I think the issue here is that the client is taking an arbitrary element of the "allowed" capabilities as the default:

    _storage.guidedCapability ??= _targets
        ?.whereType<GuidedStorageTargetReformat>()
        .expand((t) => t.allowed)
        .toSet()
        .firstOrNull;

It shouldn't do that.

https://github.com/canonical/subiquity/pull/1774 seems to help, but as a set is used in u-d-i, the order is not certain to be preserved. Better to fix on u-d-i side.

https://github.com/canonical/ubuntu-desktop-provision/pull/107 for the other side

root cause - in install-sources.yaml, enhanced-secureboot listed first, so the info objects were in that order, so we add the capability flags in that order, so the CORE_BOOT flag was there first.

fixed by:
subiquity - set it up so DIRECT is offered first, if it's going to be an option
u-d-i - drop the usage of a set - subiquity already is doing the same by checking if the flag is already in the list, so there should not be a redundant flag - then default to the first flag offered