RFR: 8349135: Add tests for HttpRequest.Builder.copy() [v4]

[Daniel Fuchs]

On Tue, 4 Feb 2025 11:07:09 GMT, Volkan Yazici <vyazici at openjdk.org> wrote:

>> Adds `HttpRequest.Builder::copy` tests to `HttpRequestBuilderTest`.
>
> Volkan Yazici has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Replace `assert`s with explicit checks throwing `AssertionError`s

Marked as reviewed by dfuchs (Reviewer).

Approved on the condition that the expected / actual mismatches are fixed.

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PR Review: https://git.openjdk.org/jdk/pull/23415#pullrequestreview-2592649195
PR Comment: https://git.openjdk.org/jdk/pull/23415#issuecomment-2633731487