[AutoScheduler] Fix task extraction with TE compiler

[comaniac]

Per discussion in https://discuss.tvm.apache.org/t/te-compiler-device-type-error-in-updatemainworkspacesize/10536/5, the updated TE compiler has a different behavior as the old compile engine in terms of visiting each Relay function for compilation. Specifically, TE compiler now makes sure the function name is unique when it appears multiple times in a model. This breaks the current task extraction mechanism, which uses function name and TE compute hash as the key to de-duplicate tasks. As a result, the same task will be extracted multiple times, and all tasks have the weight 1.

This PR makes the following changes to resolve this issue:

1. Change the type of wkl_key_to_weight from Dict[str, int] to Dict[str, Tuple[int, Set[Str]]], mapping from a workload key to the weight as well as associated function names. In this way, we guarantee that functions with the same TE compute will be extracted once.
2. Add func_name_to_wkl_key, mapping from the unique function name to its workload key. When TE compiler is used and te_compiler_update_weights is invoked, it obtains the workload key of the given function and aggregate the weights.
3. Refactor unit tests to be pytest parameterized. Also improve the control flow test to have 2 identical Conv2Ds. Without this PR, this test will fail because it falls back to use VM compiler due to the control flow and extracts 2 identical tasks.

cc @masahi @csullivan @jroesch @merrymercy

[jcf94]

Thanks! @comaniac