refactor(vm): rename filesystemReady condition to filesystemFrozen

[eofff]

Description

Why do we need it, and what problem does it solve?

What is the expected result?

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: <scope name in kebab-case (See CONTRIBUTING.md#scope)>
type: fix | feature | chore
summary: <ONE-LINE of what effectively changes for a user>