Alert rule: make calculation minutes selection a dropdown

[pvgennip]

We would like encourage users not to parse rules too often. Please set the default at 3 hours.

Replace the minute stepper with dropdown with these options:

• 15 min
• 30 min
• 1 hour
• 3 hours
• 6 hours
• 12 hours
• 24 hours
• 48 hours

[JuliaBD]

Tbt on test