[foreign-memaccess+abi] RFR: 8292957: Remove redundant MemoryLayout::is* methods [v2]

[Athijegannathan Sundararajan]

On Fri, 26 Aug 2022 09:18:45 GMT, Per Minborg <duke at openjdk.org> wrote:

>> This PR removes the public API methods `MemoryLayout::isPadding`, `GroupLayout::isStruct`, and `GroupLayout::isSequence`. Now that the `MemoryLayout` sealed hierarchy provides the same information, these redundant methods should be removed for reasons of consistency, symmetry, brevity, and simplicity.
>> 
>> See the details and proposed replacements in https://bugs.openjdk.org/browse/JDK-8292957
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Revoke import optimizations

Marked as reviewed by sundar (Committer).

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PR: https://git.openjdk.org/panama-foreign/pull/714