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

[Ioi Lam]

On Thu, 15 Oct 2020 22:07:46 GMT, Claes Redestad <redestad 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.

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Marked as reviewed by iklam (Reviewer).

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