RFR: 8308655: Narrow types of ConstantPool and ConstMethod returns [v2]

[Coleen Phillimore]

On Wed, 24 May 2023 18:19:33 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> This change uses a number of ways to eliminate -Wconversion warnings in the metadata files in the oops directory. 
>> 
>> 1. narrow return types to u2 if the accessor is for a field or value that's u2 (u2 is most common for constMethod fields and constant pool indices)
>> 2. Use checked_cast<type> for places where we know the int value is u2 or s2 but propagating these types is too much fan out.
>> 3. Use plain casts where it's obvious that the int value fits in the casted-to type.
>> 4. Moved KlassKind to be contained in Klass to add the Unknown enum value to use instead of -1.
>> 5. Moved the compute_from_signature function into ConstMethod as it sets values in ConstMethod and the parameters are changed in the set functions.  Removed some pass through functions in Method.
>> 
>> Tested with tier1-4.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fred's comments.

Matias, thank you for the review and comments.

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PR Review: https://git.openjdk.org/jdk/pull/14092#pullrequestreview-1442665615