RFR: 8369441: Two container tests fail after JDK-8292984

[Severin Gehwolf]

Please review this simple test fix to the some container tests which currently fail. `TestJFREvents.java` fails because it was relying on a log line at the trace level in order to parse the total machine memory from it and use in the test. We should instead not rely on the log line but use the existing Whitebox API to query that info. `TestMemoryAwareness.java` fails because it matches a log line that was changed in JDK-8292984.

Updating both tests fix the problems.

**Testing:**
- [x] GHA (not really useful for this as the touched tests don't run and it touches nothing else)
- [x] Ran the affected container tests locally on Linux x86_64 (cg v2). Fail before this fix, pass after.

Thanks,
Severin

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Commit messages:
 - 8369441: Two container tests fail after JDK-8292984

Changes: https://git.openjdk.org/jdk/pull/27699/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27699&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8369441
  Stats: 21 lines in 2 files changed: 3 ins; 13 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/27699.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27699/head:pull/27699

PR: https://git.openjdk.org/jdk/pull/27699