RFR: 8370943: Support heap expansion during startup in Serial and Parallel

[Thomas Schatzl]

On Thu, 30 Oct 2025 11:41:20 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Add heap expansion logic in allocation slow-path during startup. Some asserts are relaxed to be used by java-threads and outside of safepoint.
> 
> Test: tier1-5

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/28059#pullrequestreview-3402997828