Use debug_name by default for instances

[leonardt]

This PR changes the default naming scheme for instances.

Before, we would generate a unique name inst{n} where n is equal to the current number of instances in the definition. This makes it challenging to debug because you have to look at the instantiation to figure out what module was being instances (which is not always obvious).

@priyanka-raina suggested that we attach module names to instances so we can see which module is being instanced (which in turn attaches the module names to the wires). We already had this logic for error message so it was fairly simple to repurpose.

The new naming scheme is: {module_name}_inst{n} where n is the number of times module_name has been instanced in the current definition.

This shouldn't affect any functionality, it should improve debugging experience, however it is a pain for any existing gold files. I've updated the magma golds here, mantle will also need to be updated.

Let me know if you have any issues with this new proposed naming scheme.

[coveralls]

Pull Request Test Coverage Report for Build 1298

• 8 of 8 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 72.08%

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Totals
Change from base Build 1292:	0.01%
Covered Lines:	3511
Relevant Lines:	4871

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💛 - Coveralls