…ML rules (elastic#72137)

* Move isThresholdRule predicate into our common folder

This is very similar to isMlRule, which is already used extensively and
lives at this level.

* Disable endpoint association checkbox for ML and Threshold rules

The fullWidth and isDisabled props were not used; what we want is
disabled.

* Fix react warning about nesting buttons

This removes the AdvancedSettingsAccordion in favor of a plain
EuiAccordion with buttonContent, as that seems to be all that's needed
here.

* Disable Exceptions tab on Details for ML or Threshold rules

These rule types do not currently support exceptions.

* Fix type error

Unused import