Add JacksonWarmup to pre-settle JIT

[schlosna]

Before this PR

OpenJDK could encounter pathological C2 JIT deoptimization storm in Jackson BeanPropertyWriter.java:731 leading to ~10x performance degradation and significant increases in CPU utilization.

See https://bugs.openjdk.org/browse/JDK-8330258 & https://bugs.openjdk.org/browse/JDK-8374307

OpenJDK has an open PR openjdk/jdk#28966 that may address this issue by switching from checking too_many_traps to too_many_traps_or_recompiles.

After this PR

==COMMIT_MSG==
Adds a JacksonWarmup type that serializes a representative set of payload shapes through fresh server and dialogue/client ObjectMappers (constructed via the same conjure-java factories used at runtime) so the JIT settles on the bimorphic BeanPropertyWriter.serializeAsField branch (typed vs untyped serializer) with full type-profile coverage before customer traffic perturbs it.

This works around OpenJDK C2 JIT deoptimization storm where uncommon_trap isnonnull triggers continuous deoptimization as seen in https://bugs.openjdk.org/browse/JDK-8330258 &
https://bugs.openjdk.org/browse/JDK-8374307 . The repeated deoptimization can be observed by jdk.Deoptimization JFR events at com.fasterxml.jackson.databind.ser.BeanPropertyWriter if (_typeSerializer == null) site, and then re-enters unstable_if deopt thrash on the serialization path when a perturbing workload arrives.

The warmup payloads interleave monomorphic fields (concrete types) with polymorphic fields (sealed interface + @JsonTypeInfo) in the same object so each iteration exercises both branches, letting C2 record a bimorphic profile during the warmup pass.

Warmup failures are caught and logged rather than aborting as a degraded JIT profile is preferable to refusing to serve traffic.
==COMMIT_MSG==

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Description

Adds a JacksonWarmup type that serializes a representative set of payload shapes through fresh server and dialogue/client ObjectMappers (constructed via the same conjure-java factories used at runtime) so the JIT settles on the bimorphic BeanPropertyWriter.serializeAsField branch (typed vs untyped serializer) with full type-profile coverage before customer traffic perturbs it.

This works around OpenJDK C2 JIT deoptimization storm where uncommon_trap isnonnull triggers continuous deoptimization as seen in https://bugs.openjdk.org/browse/JDK-8330258 &
https://bugs.openjdk.org/browse/JDK-8374307 . The repeated deoptimization can be observed by jdk.Deoptimization JFR events at com.fasterxml.jackson.databind.ser.BeanPropertyWriter if (_typeSerializer == null) site, and then re-enters unstable_if deopt thrash on the JSON serialization path when a perturbing workload arrives.

The warmup payloads interleave monomorphic fields (concrete types) with polymorphic fields (sealed interface + @JsonTypeInfo) in the same object so each iteration exercises both branches, letting C2 record a bimorphic profile during the warmup pass.

Warmup failures are caught and logged rather than aborting as a degraded JIT profile is preferable to refusing to serve traffic.

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💡 Improvements

• Adds a JacksonWarmup type that serializes a representative set of payload shapes through fresh server and dialogue/client ObjectMappers (constructed via the same conjure-java factories used at runtime) so the JIT settles on the bimorphic BeanPropertyWriter.serializeAsField branch (typed vs untyped serializer) with full type-profile coverage before customer traffic perturbs it.

  This works around OpenJDK C2 JIT deoptimization storm where uncommon_trap isnonnull triggers continuous deoptimization as seen in https://bugs.openjdk.org/browse/JDK-8330258 &
  https://bugs.openjdk.org/browse/JDK-8374307 . The repeated deoptimization can be observed by jdk.Deoptimization JFR events at com.fasterxml.jackson.databind.ser.BeanPropertyWriter if (_typeSerializer == null) site, and then re-enters unstable_if deopt thrash on the JSON serialization path when a perturbing workload arrives.

  The warmup payloads interleave monomorphic fields (concrete types) with polymorphic fields (sealed interface + @JsonTypeInfo) in the same object so each iteration exercises both branches, letting C2 record a bimorphic profile during the warmup pass.

  Warmup failures are caught and logged rather than aborting as a degraded JIT profile is preferable to refusing to serve traffic. (#3512)