[Rev 01] RFR: 6674: Use try-with-resource in more places and close un-closed resources

[Henrik Dafgård]

> This PR fixes a few places where we didn't close resources properly before and also changes a number of older usages of IOToolkit to instead use try-with-resource.

The pull request has been updated with 1 additional commit.

-------------

Added commits:
 - be2d6092: Fix formatting in core

Changes:
  - all: https://git.openjdk.java.net/jmc/pull/33/files
  - new: https://git.openjdk.java.net/jmc/pull/33/files/3d150a42..be2d6092

Webrevs:
 - full: https://webrevs.openjdk.java.net/jmc/33/webrev.01
 - incr: https://webrevs.openjdk.java.net/jmc/33/webrev.00-01

  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jmc/pull/33.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/33/head:pull/33

PR: https://git.openjdk.java.net/jmc/pull/33