Strenght Precedence Rules
When multiple drivers are driving a signal, two strenghts are
considered at a time (the output of two processes).
The order in which these strengths are considered does not
affect the outcome because there is a strong ordering in the
resolution_table: U > X > 0, 1 > W > L, H > -.
Thus once a signal is partially resolved to a given value,
it is never further resolved to a weaker value.
A 0/1 and L/H conflict always resolve to a stronger undefined