RFR: 8274679: Remove unnecessary conversion to String in security code in java.base

[Andrey Turbanov]

Cleanup unnecessary String.valueOf calls (and similar) when conversion will happen implicitly anyway.

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Commit messages:
 - [PATCH] Remove unnecessary conversion to String in security code in java.base

Changes: https://git.openjdk.java.net/jdk/pull/5798/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5798&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274679
  Stats: 57 lines in 14 files changed: 0 ins; 8 del; 49 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5798.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5798/head:pull/5798

PR: https://git.openjdk.java.net/jdk/pull/5798