RFR: 8314746: Remove unused private put* methods from DirectByteBufferR

[Andrey Turbanov]

1. private ByteBuffer putChar(long a, char x)
2. private ByteBuffer putShort(long a, short x)
3. private ByteBuffer putInt(long a, int x)
4. private ByteBuffer putLong(long a, long x)
5. private ByteBuffer putFloat(long a, float x)
6. private ByteBuffer putDouble(long a, double x)

This methods are only called from this fragment and calls are guarded by `#if[rw]`
https://github.com/openjdk/jdk/blob/17a19dc06062331c954fa519a4f668664b1533c9/src/java.base/share/classes/java/nio/Direct-X-Buffer-bin.java.template#L61-L82

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Commit messages:
 - [PATCH] Remove unused methods from DirectByteBufferR

Changes: https://git.openjdk.org/jdk/pull/15365/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15365&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314746
  Stats: 7 lines in 1 file changed: 2 ins; 4 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15365.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15365/head:pull/15365

PR: https://git.openjdk.org/jdk/pull/15365