[foreign-memaccess+abi] RFR: Add stack walk test case that doesn't verify oops

[Jorn Vernee]

On Wed, 16 Dec 2020 14:25:45 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> This is a followup for the earlier quickfix of: https://github.com/openjdk/panama-foreign/pull/417
> 
> This adds another test case to TestStackWalk that catches the failing code path.
> 
> This re-uses the previously added `WhiteBox::verifyFrames`, and adds a flag to turn off the verification, which triggers the problematic code path. (I've also renamed this to just `walkFrames`, since now we don't always do verification anymore.

I've integrated all open comments now (including offline discussion), please have another look. Thanks.

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PR: https://git.openjdk.java.net/panama-foreign/pull/423