[18.0][ADD] base_tier_validation_delegation

[astirpe]

This is a proposal to add an initial module, part of a suite of modules, to allow users to delegate tier validation operations to another user when they are out of the office.

Here is a list of potential future modules:

base_tier_validation_delegation (Core)
base_tier_validation_delegation_log (Logging & Auditing) #1268
base_tier_validation_delegation_hr (HR) #1269
base_tier_validation_delegation_policy (Administrative Policies)
base_tier_validation_delegation_rule (Model-Specific Rules)