[jdk17u-dev] RFR: 8275079: Remove unnecessary conversion to String in java.net.http

[Goetz Lindenmaier]

I backport this to simplify later backports.
There will be a larger set of backports to http2 and similar.

Skipped Copyrights in Http1Response and Http1Request
as they were already adapted to a later value.

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Commit messages:
 - Backport 19f76c215dbe9528dde10acd744be54618ea5e4c

Changes: https://git.openjdk.org/jdk17u-dev/pull/3683/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3683&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8275079
  Stats: 32 lines in 13 files changed: 0 ins; 3 del; 29 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3683.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3683/head:pull/3683

PR: https://git.openjdk.org/jdk17u-dev/pull/3683