Honor @JsonValue accessor format with explicit serializers

[jin-sungdae]

When a @jsonvalue accessor has both an explicit serializer and @jsonformat, the accessor's format is ignored. For example:

static class Value {
    @JsonValue
    @JsonSerialize(using = JavaUtilDateSerializer.class)
    @JsonFormat(pattern = "yyyy-MM", timezone = "UTC")
    public Date value = new Date(0L);
}

On current 3.x, serializing this value produces "1970-01-01T00:00:00.000Z" instead of "1970-01".

#6076 added an accessor-backed BeanProperty for dynamically or statically resolved @jsonvalue serializers, but the already-supplied serializer branch still contextualizes against only the enclosing property (or null at the root). Use the same _accessorProperty helper in that branch, preserving the existing enclosing-property precedence.

This is a follow-up to #4762 / #6076 and targets 3.x, where that helper is available. It does not introduce another annotation-merging implementation or change public APIs.

Regression coverage:

• Explicit serializer on a @jsonvalue field.
• Explicit serializer on a @jsonvalue method.
• Nested wrapper without an enclosing format override.
• Enclosing format override retaining precedence.

Validation on Microsoft OpenJDK 17.0.15 / Maven 3.9.9:

• Before the fix: the new test class runs 4 tests, with 3 failures; the enclosing-override control already passes.
• Focused run: 28 tests, 0 failures/errors/skips.
• mvn -B -ntp clean verify: BUILD SUCCESS; 7,475 tests, 0 failures, 0 errors, 1 skipped.
• git diff --check passes.

Prepared with AI assistance. The failure reproduction and verification commands above were executed locally.

[gitar-bot]

Code Review ✅ Approved

🟡 Medium risk

Fixes @JsonValue accessor format being ignored when an explicit serializer is also present by using the same accessor-property helper for already-supplied serializers. Comprehensive regression coverage validates the fix across field and method accessors, nested wrappers, and enclosing format precedence. No issues found.

Review coverage

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[cowtowncoder]

Thank you for submitting this PR; I'll review it as soon as I have time.

One thing needed before merging is CLA (if not yet sent); see https://github.com/FasterXML/jackson/blob/main/CONTRIBUTING.md#paperwork for details.

Looking forward to merging the pr !

[github-actions]

🧪 Code Coverage Report

Metric	Coverage	Change
Instructions	82.48%	📉 -0.010%
Branches	76.32%	📉 -0.030%

Coverage data generated from JaCoCo test results