RFR: 8276429: CodeHeapState::print_names() fails with "assert(klass->is_loader_alive()) failed: must be alive"

[Evgeny Astigeevich]

This PR fixes `applications/kitchensink/Kitchensink.java` regression introduced by JDK-8275729.
The requirement for a method holder to be alive is relaxed to the holder not to be NULL.
If holder's name is not available the format of the string used for the name is the same as for unavailable method's name and signature, instead of the default string: `<unknown>`.
Testing:
- `make run-test TEST=tier1_serviceability`: Passed
- `make run-test TEST=hotspot_tier2_serviceability`: Passed
- `make run-test TEST=serviceability/dcmd/compiler/CodeHeapAnalyticsMethodNames.java`: Passed

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Commit messages:
 - 8276429: CodeHeapState::print_names() fails with "assert(klass->is_loader_alive()) failed: must be alive"

Changes: https://git.openjdk.java.net/jdk/pull/6234/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6234&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276429
  Stats: 5 lines in 1 file changed: 1 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6234.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6234/head:pull/6234

PR: https://git.openjdk.java.net/jdk/pull/6234