RFR: 7979: Reduce allocation rate in ParserStats

[Richard Startin]

On Wed, 23 Nov 2022 19:12:48 GMT, Jean-Philippe Bempel <jpbempel at openjdk.org> wrote:

> Thanks, LGTM
> 
> As we are in 9 branch, could we consider including a lib like fastutil for dealing better with primitives collections?

I'm not sure that would help here, as concurrency support is required, but it would help if the fallback in `FastAccessNumberMap` could be swapped out for something that doesn't box the constant identifiers (or if there were just no fallback at all and the paginated array could just grow indefinitely)

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PR: https://git.openjdk.org/jmc/pull/455