RFR: 8314684: Add overview docs to loaderConstraints.cpp [v3]

[Calvin Cheung]

On Tue, 22 Aug 2023 22:07:47 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> I added some documentation to make it easier to understand loaderConstraints.cpp. Please review and check if my description is actually correct. Thanks!
>
> Ioi Lam has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - added references to source code
>  - added info about ConstraintSet

Marked as reviewed by ccheung (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/15372#pullrequestreview-1590721829