[Relay] Make DeviceAnalyzer a mixed mode visitor

[masahi]

Closes #10135

There are about 5 visitors / mutators in device_planner.cc, but only one of them is mixed mode for now following @mei-ye's original PR.

@mei-ye Please confirm if this fixes the issue on windows.

cc @mbrookhart @mbs-octoml @tmoreau89

One issue with making DeviceAnalyzer inherit from MixedModeVisitor is the intermediate tuple in call_lowered op, as in

%0 = on_device(%x, constrain_body=False) /* from_string */ /* ty=Tensor[(128, 128), float32] */;
%1 = on_device(%y, constrain_body=False) /* from_string */ /* ty=Tensor[(128, 128), float32] */;
%2 = on_device(%z, constrain_body=False) /* from_string */ /* ty=Tensor[(128, 128), float32] */;
%3 = (%0, %1, %2);
call_lowered(@gem, %3) /* from_string */ /* ty=Tensor[(128, 128), float32] */ 

If we do pure post-DFS traversal, the tuple will be visited before call_lowered, and that makes all original CallNode args unify to the domain of the tuple. The solution we agreed upon is to update ExpandDataflow function to ignore that tuple when it expands call_lowered op.

[masahi]

@mbs-octoml I assume this is ok to remove.

[mbs-octoml]

Oh yeah, thanks.

[mbrookhart]

LGTM

[tmoreau89]

Thank you @mbrookhart and @masahi - PR has been merged.

[mei-ye]

I confirmed that this fixes the issue I saw on windows. Thanks!