parser: track permstable32 support as a version

Track permstable32 as an explicit version instead of split bool/v1 flags.

Replace kernel_supports_permstable32_v1 with kernel_supports_permstable32_version and probe version feature nodes 0x000003, 0x000002 and 0x000001.

Treat kernels that expose policy/permstable32 without a version node as unsupported (-1), and keep kernel_supports_permstable32 as a derived usability flag so v1 and unversioned kernels stay disabled.

Update prompt_compat_mode_supported() to require permstable32 version >= 2 for permsv2 mode.

Signed-off-by: Zygmunt Krynicki zygmunt.krynicki@canonical.com