RFR: 8354724: BufferedReader readAllLines and readString methods [v4]

[Brian Burkhalter]

On Thu, 17 Apr 2025 22:13:06 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Implement the requested methods and add a test thereof.
>
> Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8354724: Change the test to reuse a ByteBuffer when writing the file

I moved `readString` to `Reader` but left its regression test in `java/io/BufferedReader/ReadAll.java`.

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PR Comment: https://git.openjdk.org/jdk/pull/24728#issuecomment-2814176144