[jdk11u-dev] RFR: 8254782: Fix benchmark issues in java/lang/StringIndexOfChar.java benchmark

[Dmitry Chuyko]

This is a follow-up to https://github.com/openjdk/jdk11u-dev/pull/41.
Original patch aplies cleanly after JDK-8254775.

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Commit messages:
 - [PATCH] Backport 72ff8e2118b94171181f017d99a861899dbf3646
 - [PATCH] Backport 96a1f08e80e40616aa8e30532b678145baf7a3a7
 - [PATCH] Backport f71e8a61988cc9f095a4f034636baf04c3f48f77

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/45/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=45&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254782
  Stats: 610 lines in 15 files changed: 592 ins; 0 del; 18 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/45.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/45/head:pull/45

PR: https://git.openjdk.java.net/jdk11u-dev/pull/45