RFR: 8234532: Remove ThreadLocalAllocBuffer::_fast_refill_waste since it is never set [v3]

[Albert Mingkun Yang]

> It has some cascading effect; two performance variables, `fastWaste` and `maxFastWaste`, can be removed also.

Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:

  review

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3756/files
  - new: https://git.openjdk.java.net/jdk/pull/3756/files/867bbe14..dcaff0bb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3756&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3756&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3756.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3756/head:pull/3756

PR: https://git.openjdk.java.net/jdk/pull/3756