Fix #5742: prevent @JsonSetter(contentNulls) propagation into nested containers

[dlwldnjs1009]

Summary

@JsonSetter(contentNulls = Nulls.FAIL) on nested container properties such as
List<List<String>> incorrectly rejects [[null]]. Only [null] (null
immediate content of the annotated container) should be rejected.

The root cause is that container deserializers pass the same BeanProperty into
nested content deserializer contextualization, so deeper container levels read
the outer property's annotation-level contentNulls.

Changes

• Add _contentProperty() in StdDeserializer to create a derived
  BeanProperty view for nested content contextualization that strips only the
  outer property's explicit annotation-level contentNulls.
• Recompute nested contentNulls from the nested content type's
  ConfigOverride or global default.
• Add _ContentBeanProperty, a lightweight delegating wrapper that preserves the
  original property identity (name/member/type) and overrides only metadata
  relevant to nested content-null handling.
• Apply to the container deserializer paths covered by the reported reproduction
  and closely related nested-container cases: CollectionDeserializer,
  MapDeserializer, EnumMapDeserializer, and ObjectArrayDeserializer.

Properties without explicit @JsonSetter(contentNulls=...) retain existing
behavior, including ConfigOverride-only and global-default-only cases.

Scope & Known Gaps

This fix is intentionally scoped to the container deserializer paths involved in
the reported issue and closely related nested-container cases.

ReferenceTypeDeserializer (used by Optional, AtomicReference) and
MapEntryDeserializer follow the same general pattern, but are left for
follow-up to keep this PR focused on #5742.

Test plan

• Field-based, creator-based, and Java record nested List tests
• Nested Map<String, List<String>>, EnumMap, and String[][]
• Regression: ConfigOverride-only and global-default-only behavior unchanged
• Cross-config: annotation FAIL + global SKIP, annotation FAIL + ConfigOverride SKIP
• ./mvnw clean verify passes

[github-actions]

🧪 Code Coverage Report

Metric	Coverage	Change
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Branches	74.43%	📈 +0.020%

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[github-actions]

🧪 Code Coverage Report

Metric	Coverage	Change
Instructions	81.27%	📉 -0.010%
Branches	74.44%	📈 +0.020%

Coverage data generated from JaCoCo test results