RFR: 8320370: NMT: Change MallocMemorySnapshot to simplify code. [v3]

[Thomas Stuefe]

On Thu, 23 Nov 2023 11:12:23 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Hi,
>> 
>> `MallocMemorySnapshot` used to be initialized in a quite non-standard way, using global placement new on an array of `size_t` of the size required to fit `MallocMemorySnapshot`. This looks like it was intended to circumvent some `ResourceObj` internals, but I'm unsure of its purpose. This change does what you expect a regular initialization of a global variable to look like.
>> 
>> ~Currently running through tier1.~ GHA passed and so did tier1 on Oracle CI.
>
> Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove AnyObj inheritance

I'm fine with it either way, but would prefer the object not to inherit from anything if its only used inline or as stack object. In any case, lets ship this.

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PR Comment: https://git.openjdk.org/jdk/pull/16724#issuecomment-1835470357