RFR: 8367976: Validate and clamp jdk.httpclient.bufsize [v6]

[Volkan Yazici]

> Validate and clamp the value populated from the `jdk.httpclient.bufsize` system property. Added two new tests: Does clamping work? Does the minimum value wedge the client?

Volkan Yazici has updated the pull request incrementally with two additional commits since the last revision:

 - Document the rationale for a separate process in `BufferSizePropertyClampTest`
 - Convert `BufferSize1Test` to JUnit

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27874/files
  - new: https://git.openjdk.org/jdk/pull/27874/files/92f07382..b9186533

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27874&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27874&range=04-05

  Stats: 50 lines in 2 files changed: 21 ins; 9 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/27874.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27874/head:pull/27874

PR: https://git.openjdk.org/jdk/pull/27874