Fix warning injected into user code by @chiselName

[jackkoenig]

In Scala 2.13, Auto-application to () is deprecated. Any nullary
method (ie. a method with no arguments) that is defined with () must now
be called with (). @chiselName used to inject a case of this warning
into user code which would then cause a warning on the @chiselName macro
that the user has no way to fix.

To see this warning, compile Chisel with Scala 2.13, you'll see something like:

[warn] .../chisel3/src/main/scala/chisel3/util/Arbiter.scala:119:2: Auto-application to `()` is deprecated. Supply the empty argument list `()` explicitly to invoke method length,
[warn] or remove the empty argument list from its definition (Java-defined methods are exempt).
[warn] In Scala 3, an unapplied method like this will be eta-expanded into a function.
[warn] @chiselName
[warn]  ^
[warn] .../chisel3/src/main/scala/chisel3/util/Arbiter.scala:135:2: Auto-application to `()` is deprecated. Supply the empty argument list `()` explicitly to invoke method length,
[warn] or remove the empty argument list from its definition (Java-defined methods are exempt).
[warn] In Scala 3, an unapplied method like this will be eta-expanded into a function.
[warn] @chiselName
[warn]  ^
[warn] two warnings found

This changes fixes this bug.

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
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Type of Improvement

• bug fix

API Impact

No impact

Backend Code Generation Impact

No impact

Desired Merge Strategy

• Squash

Release Notes

Fix Scala 2.13 warning "Auto-application to () is deprecated." when using @chiselName in user code.

Reviewer Checklist (only modified by reviewer)

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• Did you mark the proper milestone (Bug fix: 3.4.x, [small] API extension: 3.5.x, API modification or big change: 3.6.0)?
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[jackkoenig]

I think CI is failing due to chipsalliance/treadle#407

[ekiwi]

I think CI is failing due to chipsalliance/treadle#407

Yes. I think we need to rebuild and republish everything against the new version of the JSON library in the correct order.

[jackkoenig]

Yes. I think we need to rebuild and republish everything against the new version of the JSON library in the correct order.

All that was needed it seems was treadle. I've republished it's SNAPSHOTs.