8362239: Reconcile enter_internal and reenter_internal in the ObjectMonitor code

[toxaart]

Hi please consider the following changes:

in this PR enter_internal() and reenter_internal() methods of the ObjectMonitor are reconciled into a single enter_internal() method, which handles both paths depending on the 2nd argument.

Tested in tiers 1-3.

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Progress

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Issue

• JDK-8362239: Reconcile enter_internal and reenter_internal in the ObjectMonitor code (Enhancement - P4)

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