RFR: 8311077: Fix -Wconversion warnings in jvmti code [v3]

[Coleen Phillimore]

On Thu, 29 Jun 2023 17:29:50 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Please review change for mostly fixing return types in the constant pool and metadata to fix -Wconversion warnings in JVMTI code.  The order of preference for changes are: 1. change the types to more distinct types (fields in the constant pool are u2 because that's their size in the classfile), 2. add direct int casts if the value has been checked in asserts above, and 3. checked_cast<> if not verified, and 4. added some pointer_delta_as_ints where needed.
>> Tested with tier1-4.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add a comment about u1 cast to new_index for the ldc bytecode.

Thanks for your comments Matias.  Some of the changes that I didn't make were because Wconversion didn't complain and where I could avoid casting.  I think more precise types for constant pool indices and cpCache indices might be more pervasive than we want and might cause more warnings down the line.  So I avoided them.

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PR Review: https://git.openjdk.org/jdk/pull/14710#pullrequestreview-1505961331