[FEATURE] Support --no-generate for terramate experimental clone

[cwe1ss]

Is your feature request related to a problem? Please describe.
We use some template stacks to reduce boilerplate that we can't/don't want to handle via globals. When running terramate experimental clone, Terramate immediately calls "terramate generate". However, we would like to do some more post-processing before actually running "terramate generate".

Describe the solution you'd like
Support the flag --no-generate (which already exists for terramate create) for terramate experimental clone. When it is set, Terramate should not invoke code generation after the stack has been cloned.