Fix #6144: withCreatorVisibility(ANY) now enables private scalar delegating constructors

[seonwooj0810]

Problem

FasterXML/jackson-databind#6144

In Jackson 3, implicit single-arg (scalar) constructors (String, long, etc.) used as
delegating creators go through _removeNonVisibleCreators, which checks
isScalarConstructorVisible against the new scalarConstructorMinLevel axis (defaulting to
NON_PRIVATE).

When users migrate from Jackson 2 — where creator visibility defaulted to ANY — the natural
fix attempt is changeDefaultVisibility(vc -> vc.withCreatorVisibility(Visibility.ANY)).
This has no effect on scalar constructors because withCreatorVisibility does not touch
_scalarConstructorMinLevel, leaving private scalar constructors still filtered out.

Repro

static class OneOf {
    public long longValue;
    public String stringValue;
    public OneOf() {}
    private OneOf(long v)   { this.longValue = v; }
    private OneOf(String v) { this.stringValue = v; }
}

// Works in Jackson 2, fails in Jackson 3 with default settings:
ObjectMapper mapper = JsonMapper.builder()
    .changeDefaultVisibility(vc -> vc.withCreatorVisibility(Visibility.ANY))
    .build();

OneOf fromLong = mapper.readValue("42", OneOf.class); // MismatchedInputException

Fix

In POJOPropertiesCollector._removeNonVisibleCreators, for single-arg constructors, accept when
either isScalarConstructorVisible or isCreatorVisible passes:

visible = _visibilityChecker.isScalarConstructorVisible(ctor.creator())
        || _visibilityChecker.isCreatorVisible(ctor.creator());

This means:

• Default behaviour unchanged: both isScalarConstructorVisible (NON_PRIVATE) and
  isCreatorVisible (PUBLIC_ONLY) return false for private constructors — they are still
  filtered out.
• withCreatorVisibility(ANY) now works: isCreatorVisible returns true for private
  constructors, so they are kept — restoring Jackson 2 migration behaviour.
• withScalarConstructorVisibility(ANY) continues to work as before.

Tests

Added testPrivateLongDelegatingCtorWithCreatorVisibilityAny to TestAutoDetect:

• Verifies that with default settings, private scalar constructors are still filtered (no
  regression).
• Verifies that with withCreatorVisibility(ANY), both private long and private String
  constructors work as implicit delegating creators.

All existing TestAutoDetect tests pass.

Note: This fix was authored with the assistance of Claude AI (Anthropic).

[cowtowncoder]

I am not sure this is correct -- Scalar creator visibility check should be used in 3.x, not general-purpose one (unlike in 2.x).

That is: VisibilityChecker.withScalarConstructorVisibility() is to be used with scalar-delegating constructors

Will add a note on #6144.