RFR: 8313249: Fix -Wconversion warnings in verifier code [v2]

[Dean Long]

On Fri, 28 Jul 2023 22:13:08 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> See bugid for comments.  Most of the verifier code deals with ints, so the u2 and other parameters weren't really needed and can be promoted to int. Mostly types are changed, but a few checked_cast<>s are added.
>> Tested with tier1-4, sanity Oracle platforms.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Ioi's suggested changes.

I also tried making _code_length and _offset u2, which seems to work, but of course there's more fan out.

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PR Comment: https://git.openjdk.org/jdk/pull/15056#issuecomment-1656537938