Fix PyROS Subordinate Optimizer Solve Time Access Routines

[shermanjasonaf]

Fixes #2441 .

Summary/Motivation:

PyROS currently attempts to access subordinate optimizer solve times through the custom-written routine pyros.util.get_time_from_solver invoked on a SolverResults object. However, this routine is prone to an exception in the event the SolverResults.solver attribute has no time attribute (particularly if the SolverResults object was returned by a subsolver interface not linked to GAMS).

Changes proposed in this PR:

• Redefine pyros.util.get_time_from_solver to more gracefully handle SolverResults objects with potentially no timing attributes
• Estimate subordinate optimizer solve times using the Pyomo TicTocTimer (for use in event the subordinate optimizer does not write a measure of the solve time to the SolverResults object)

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