RFR: 8286560: Remove user parameter from jdk.internal.perf.Perf.attach() [v2]

[Ioi Lam]

> The API `jdk.internal.perf.Perf.::attach(String user, int lvmid)` is never used. It should be removed, and all the handling of a specified user name should be removed.

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

  @AlanBateman comments - remove thros IllegalArgumentException clause

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8669/files
  - new: https://git.openjdk.java.net/jdk/pull/8669/files/afa66232..0b73a9d4

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8669&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8669&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 2 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8669.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8669/head:pull/8669

PR: https://git.openjdk.java.net/jdk/pull/8669