Could not find field with name 'virtual' in reader for 'thread'

[thurka]

Steps to reproduce:

1. Open JFR snapshot from dev. build of JDK 21 (jfr-1685451518486.jfr.gz)
2. There is warning in the messages.log:

WARNING [org.openjdk.jmc.flightrecorder.internal.parser.v1.ValueReaders$ReflectiveReader]: Could not find field with name 'virtual' in reader for 'thread'

This is likely caused by JFR support of Virtual Threads JEP 444.

[thurka]

Similar issue reported against JMC: https://bugs.openjdk.org/browse/JMC-7863