Smart Contracts: Do not schedule an interval tick if there is a datetime tick at the same time

[bchamagne]

Description

This is required for #929. I extracted it from there.
Currently, when there is one interval trigger that ticks at the same time at as datetime trigger. They both run concurrently but only 1 can actually create the transaction. The other will get a transaction already mining issue.
This PR fix this by not scheduling an interval tick if there is a datetime tick.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Manual test with this contract:

@version 1

condition inherit: [ content: true ] 

actions triggered_by: interval, at: "* * * * *" do 
  Contract.set_content("interval")
end

actions triggered_by: datetime, at: 1683272596 do 
  Contract.set_content("datetime")
end

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules