Only allow mongo upgrade when featureCompatibilityVersion is already set in Mongo CR

[andrercm]

potential customer issue caused by:

• initially deployed MongoDB 4.2
• upgraded to 4.4 at some point (before we added all the new logic for upgrading to MongoDB 5)
• an upgrade to MongoDB 5 was attempted but the feature compatibility was never moved to 4.4

We need to have a solid check to make sure the feature compatibility is set to 4.4 before attempting the upgrade to 5
We are setting featureCompatibilityVersion now but in the past we didn't. That is the only scenario I can think of that would have caused this.

[sanjayprab]

Added a check - #1544 which makes sure featureCompatibilityVersion is present before upgrading to 5 or greater