[DistConv] MIOpen path through convolution algorithm selection

[benson31]

Currently, any value for the "name" passed to get_{fwd,bwd_{data,filter}}_algorithm() (e.g., here) that is not "AUTOTUNE" will probably fail for one reason or another.

"HEURISTIC" will fail because this isn't supported in MIOpen. Other options will fail because MIOpen requires that their Find APIs be called, and we don't currently incorporate that when the algorithm is not "AUTOTUNE".

[benson31]

I don't know that a solution to this will be back-ported into DistConv (it's not impossible, but not likely), but I wanted to document this here to ensure ongoing refactors do not hit the same pitfall.

[benson31]

We should also more robustly support things like "autotune but pick a deterministic algorithm", when possible.