RFR: 8354724: BufferedReader readAllLines and readString methods [v15]

[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: Fix potential NPE in test

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24728/files
  - new: https://git.openjdk.org/jdk/pull/24728/files/dc84bd1b..db338317

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24728&range=14
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24728&range=13-14

  Stats: 2 lines in 1 file changed: 1 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