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

[Brian Burkhalter]

> 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

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24728/files
  - new: https://git.openjdk.org/jdk/pull/24728/files/4fac584c..422703fe

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24728&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24728&range=02-03

  Stats: 10 lines in 1 file changed: 9 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/24728.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24728/head:pull/24728

PR: https://git.openjdk.org/jdk/pull/24728