RFR: 8354724: BufferedReader readAllLines and readString methods [v7]

[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: readString -> readAllChars; update test

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24728/files
  - new: https://git.openjdk.org/jdk/pull/24728/files/b9424bb4..b2c3481a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24728&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24728&range=05-06

  Stats: 20 lines in 2 files changed: 11 ins; 3 del; 6 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