RFR: 8253350: Remove unimplemented SharedRuntime::clean_*_entry

[Aleksey Shipilev]

Their existence seems to predate OpenJDK. There are no uses, no definitions.

Testing:
  - [x] Linux x86_64 fastdebug build
  - [x] Text searches for `clean_*_entry` in `src/hotspot`

-------------

Commit messages:
 - 8253350: Remove unimplemented SharedRuntime::clean_*_entry

Changes: https://git.openjdk.java.net/jdk/pull/245/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=245&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253350
  Stats: 4 lines in 1 file changed: 0 ins; 4 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/245.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/245/head:pull/245

PR: https://git.openjdk.java.net/jdk/pull/245