RFR: 8307100: Remove ReferentBasedDiscovery reference discovery policy

[Kim Barrett]

On Fri, 28 Apr 2023 12:04:08 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Mostly consisting of mechanic refactoring after replacing `RefDiscoveryPolicy == ...` with `true` or `false`.
> 
> Test: tier1-6

Looks good.

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Marked as reviewed by kbarrett (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13715#pullrequestreview-1406887413