Tuners should have precondition check

[ultmaster]

Tuners should throw error in case of invalid search space, such as: {"_type": "randint", "_value": [1, 2, 3]}, or {"_type": "randint", "_value": [0.5, 1.5]}.

[chicm-ms]

@ultmaster What is current Tuners behaviour in case of invalid search space?

[ultmaster]

Sometimes they get processed as is. Sometimes tuners fail. Tuners' behaviors are undefined.

[scarlett2018]

Assign to @QuanluZhang for further triage.