Inconsistent usage of UTC & local timezones for timestamps

[iporollo]

Description

There are Inconsistent timezones being used between various data models throughout the application. Some are UTC while others are local times.

Expected behavior

Timezones should be consistent for all data models (Monitors, Jobs, Executions, Datasources, Integrations) throughout the entirety of the application.

Steps to reproduce

1. Add a data source
2. Wait until monitors are created
3. Navigate to executions page
4. Notice timestamp
5. Navigate to jobs tab on the executions page
6. Notice different timestamp
7. Navigate to the monitors page
8. Notice different timestamp