RFR: 8252546: Move ObservableValue's equality check and lazy evaluation descriptions to @implSpec [v3]

[Ambarish Rapte]

On Sat, 12 Sep 2020 14:10:38 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> Moving implementation details about lazy evaluation and equality checking to `@implSpec`.
>
> Nir Lisker has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Addressed review comments and added </li>

Marked as reviewed by arapte (Reviewer).

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PR: https://git.openjdk.java.net/jfx/pull/292