RFR: 8254855: Clean up and remove unused code in vmIntrinsics

[Vladimir Kozlov]

On Fri, 16 Oct 2020 00:12:45 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> - Remove unused code and constants
>> - Guard some code only used for assertions by ASSERT
>> - Adjust log2_FLAG_LIMIT (could have been 3 also before removing F_RNY)
>> 
>> Testing: tier1-3
>
> LGMT. I try to find the last time for_boxing() and verify_method()  were used, and they weren't even used in JDK7! So
> we have been carrying around this junk for quite a while.

vmIntrinsics::verify_method() become unused after next change:
http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/75596850f863

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PR: https://git.openjdk.java.net/jdk/pull/688