[Feature] Hypervisor upgrade plan need prompt

If you start COU by running cou upgrade to upgrade control plane and data plane at the same time. COU won't provide prompt for user to confirm if continue of not at the time when hypervisor group start.
Also no prompt between two zones.

Example output, no Continue (y/n): after mysql upgrade finished and after zone 1 finished:

Upgrade plan for 'mysql-innodb-cluster' to 'zed'
    Upgrade software packages of 'mysql-innodb-cluster' from the current APT repositories
        Ψ Upgrade software packages on unit 'mysql-innodb-cluster/0'
        Ψ Upgrade software packages on unit 'mysql-innodb-cluster/1'
        Ψ Upgrade software packages on unit 'mysql-innodb-cluster/2'
    Change charm config of 'mysql-innodb-cluster' 'source' to 'cloud:jammy-zed'
    Wait for up to 2400s for app 'mysql-innodb-cluster' to reach the idle state
    Verify that the workload of 'mysql-innodb-cluster' has been upgraded on units: mysql-innodb-cluster/0, mysql-innodb-cluster/1, mysql-innodb-cluster/2

Continue (y/n): y
Upgrade plan for 'mysql-innodb-cluster' to 'zed' executed in 95 seconds ✔
Upgrade plan for [nova-compute/0, nova-compute/2] in 'zone1' to 'zed' executed in 1005 seconds ✔
Upgrade plan for [nova-compute/1, nova-compute/5] in 'zone3' to 'zed' executed in 929 seconds ✔

Note: Since upgrade two group or two zones together won't be a common practice, this should be a low priority issue.

canonical / charmed-openstack-upgrader

[Feature] Hypervisor upgrade plan need prompt #586