Support @WithConfig on IBM J9 8 / OpenJ9 / Semeru 11 JVMs#11388
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ByteBuddy retransformation silently fails on IBM J9 / OpenJ9 / Semeru,
leaving `InstrumenterConfig.INSTANCE` / `Config.INSTANCE` as
`private static final`. `rebuildConfig()`'s `Field.set(null, ...)` then
throws for every test in the class — including ones with no `@WithConfig`
at all:
```
org.opentest4j.AssertionFailedError: expected: <true> but was: <false>
at WithConfigExtension.checkWritable(WithConfigExtension.java:331)
at WithConfigExtension.checkConfigTransformation(...:324)
at WithConfigExtension.beforeAll(...:91)
Suppressed: java.lang.AssertionError: Failed to rebuild config
at WithConfigExtension.rebuildConfig(...:295)
Caused by: java.lang.IllegalAccessException: ... InstrumenterConfig
with modifiers "private static final"
at java.lang.reflect.Field.set(Field.java:784)
at WithConfigExtension.rebuildConfig(...:291)
```
This commit keep ByteBuddy as the primary mechanism to transform bytecode
bit adds a `sun.misc.Unsafe`-based fallback:
* `makeConfigInstanceModifiable()` checks the actual field modifiers and
picks `WriteMode.REFLECTION` when retransformation worked, or
`WriteMode.UNSAFE` otherwise.
* The Unsafe mechanism is encapsulated in a `UnsafeFieldWriter` that
handle updating the field value via `Unsafe::putObjectVolatile`.
* Unsafe is resolved lazily and propagates `ReflectiveOperationException`
so a JVM without `sun.misc.Unsafe` lands in the existing
`configModificationFailed` branch.
* `ConfigInstrumentationFailedListener` now flags failures for
`InstrumenterConfig` as well, not only `Config`.
[ci: NON_DEFAULT_JVMS]
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What Does This Do
Fallback to unsafe when retransformation fail on old IBM J9 / Semeru 11 JVMs.
Motivation
Additional Notes
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