RFR: 8284780: Need methods to create pre-sized HashSet and LinkedHashSet [v11]

[XenoAmess]

> as title.

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

  rename items to elements

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8302/files
  - new: https://git.openjdk.java.net/jdk/pull/8302/files/56d029f4..4ec6ba9f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8302&range=10
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8302&range=09-10

  Stats: 12 lines in 2 files changed: 0 ins; 0 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8302.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8302/head:pull/8302

PR: https://git.openjdk.java.net/jdk/pull/8302