8331609: GenShen: Refactor generational mode allocations

[earthling-amzn]

• The code for resizing and retrying young allocation requests according to what's available in the young generation has been removed. This code became redundant after the free set was rewritten and began providing the same functionality.
• An unused field and its attendant methods were removed from ShenandoahThreadLocalData.
• The code for managing plab expenditures and configuring other plab behavior has been moved from ShenandoahHeap into ShenandoahOldGeneration.

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Progress

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Issue

• JDK-8331609: GenShen: Refactor generational mode allocations (Task - P4)

Reviewing

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[bridgekeeper[bot]]

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[openjdk[bot]]

@earthling-amzn This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8331609: GenShen: Refactor generational mode allocations

Reviewed-by: kdnilsen

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[mlbridge[bot]]

Webrevs

• 03: Full - Incremental (4320206b)
• 02: Full - Incremental (a2c52db1)
• 01: Full - Incremental (b2163411)
• 00: Full (b6860298)

[earthling-amzn]

/integrate

[openjdk[bot]]

Going to push as commit 80e69877f807499e811ff0353d7477057fa2f63d.

[openjdk[bot]]

@earthling-amzn Pushed as commit 80e69877f807499e811ff0353d7477057fa2f63d.

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