feat: spread Pod rollout

[leonardoce]

This patch adds two new parameters to the operator configuration:

• CLUSTERS_ROLLOUT_DELAY: the amount of time in seconds the operator should wait between rollouts of Pods of different clusters

• INSTANCES_ROLLOUT_DELAY: the amount of time in seconds the operator should wait between rollouts of Pods of the same cluster

Using these two parameters, the operator can be confgured to spread the rollout of new versions of PostgreSQL and of the instance manager, easing the impact of upgrading the operator or the PostgreSQL version.

Closes: #5384

[github-actions[bot]]

:exclamation: By default, the pull request is configured to backport to all release branches.

• To stop backporting this pr, remove the label: backport-requested :arrow_backward: or add the label 'do not backport'
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[armru]

/test limit=local

[github-actions[bot]]

@armru, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/10828315017

[gbartolini]

/test limit=local

[github-actions[bot]]

@gbartolini, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/10959929724

[gbartolini]

/test limit=local

[github-actions[bot]]

@gbartolini, here's the link to the E2E on CNPG workflow run: https://github.com/cloudnative-pg/cloudnative-pg/actions/runs/10970400607