Fixes #6626. Pass sym.name to sanitizeName instead of sym.name.asSimpleName

[ashwinbhaskar]

asSimpleName method on DerivedName is implemented to throw UnspportedOperationException. The class GenericSignatures's method classSig calls asSimpleName on instances of Name without checking on the actual type (DerivedName extends TermName which extends Name).
~~A check has been added to refrain calling asSimpleName if the type is DerivedName. ~~
As @smarter suggested, refrained from calling asSimpleName for all the cases because mangledString takes care of giving the name of the class in byte code and it is already being called by sanitizeName.

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[ashwinbhaskar]

Line 170: should be "name.asSimpleName" instead of "sym.name.asSimpleName".
PS. Coding style: remove space after "Unit" (line 167) and space before ":" (4 times).

done

[smarter]

See comment.

[smarter]

This PR is missing a test.

[ashwinbhaskar]

This PR is missing a test.

@smarter added test

[ashwinbhaskar]

@smarter can this be merged now?

[smarter]

If you look at other tests in generic-java-signatures like https://github.com/lampepfl/dotty/blob/master/tests/generic-java-signatures/andTypes.scala you'll see that they have a main method which prints the generic type signature of members, the output of this main method must match the corresponding check file https://github.com/lampepfl/dotty/blob/master/tests/generic-java-signatures/andTypes.check. Your test should be enhanced to contain a similar main method (you can just copy paste the one from andTypes.scala) and a check file to make sure that we output the correct signature for a

[smarter]

Thank you!