RFR: 8306456: Don't leak _worklist's memory in PhaseLive::compute [v2]

[Johan Sjölen]

> `PhaseLive::compute` used to do this: `_worklist = new (_arena) Block_List();`. This allocates the `Block_List` to the `_arena`, but the backing array is allocated on the resource area: `Block_List() : Block_Array(Thread::current()->resource_area()), _cnt(0) {}`. This causes at most 5 worklists and at least 4 worklists to be created and not freed until the compilation is finished. This patch allocates the worklist within `PhaseLive::compute`:s local resource mark.

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

  Fix style and make worklist passed in as argument

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13535/files
  - new: https://git.openjdk.org/jdk/pull/13535/files/e1191341..8c436ab9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13535&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13535&range=00-01

  Stats: 17 lines in 2 files changed: 0 ins; 3 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/13535.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13535/head:pull/13535

PR: https://git.openjdk.org/jdk/pull/13535