[IMPROVEMENT] Eventually make freeze-filesystem-for-snapshot default to true

[Eric Weber]

Is your improvement request related to a feature? Please describe (👍 if you like this request)

This is a followup to #2187 based on this investigation and especially this conclusion.

TLDR, it is not practical to make freeze-filesystem-for-snapshot the default behavior until kernels with version >= 5.17.0 are more commonplace. We should revisit this issue once every feature release to check if:

• The majority of kernels Longhorn is installed on are >= 5.17.0.
• The kernel for the Linux distro we base our container images on (currently we use SLE BCI based on SLES) ships a kernel >= 5.17.0. (Obviously our containers don't ship with a kernel, but it's seems a reasonable heuristic to not default a feature that we don't support on our own distro.)

Describe the solution you'd like

Once we decide to change the default:

• Ensure the default is true in new installations.
• Ensure upgrades do not switch the existing setting from false to true.
• Update the environment check script (and/or Longhorn CLI) to check for an appropriate kernel.