RFR: 7903321: Use a set instead of a map to record methods in class 'MethodGroup' [v3]

[Guoxiong Li]

On Wed, 21 Sep 2022 11:41:10 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix exception message.
>
> All right then!

@shipilev Thanks for the review.

-------------

PR: https://git.openjdk.org/jmh/pull/79