RFR: 8253275: Remove unused methods after CMS removal [v2]

[Aleksey Shipilev]

> Static analysis shows a few examples of methods that are not used/implemented after CMS removal. We can purge them.
> 
> Testing: text searches over the code base, no hits; Linux x86_64 builds

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Remove Generation::sample_eden_chunk() too and rewire some code

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/219/files
  - new: https://git.openjdk.java.net/jdk/pull/219/files/1b7c966f..0b131007

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=219&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=219&range=00-01

  Stats: 12 lines in 2 files changed: 0 ins; 10 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/219.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/219/head:pull/219

PR: https://git.openjdk.java.net/jdk/pull/219