Exponential validation cost: (schema node, instance node) pairs re-evaluated once per evaluation path

A 43-byte instance OOMs validate() on 3.0.6 with -Xmx2g, against a fixed 165-byte schema.

Cost is 2^depth because each (schema node, instance node) pair is re-evaluated once per evaluation
path. At depth 20 that's 2,097,152 errors covering 2 distinct (schemaLocation, instanceLocation)
pairs.

Filing as a perf issue: I checked ~600 real OpenAPI specs and none had a
request-body schema with this shape. I wouldn't rule it out completely.

Reproduce

String schema = "{\"$ref\":\"#/$defs/n\",\"$defs\":{\"n\":{\"anyOf\":["
    + "{\"type\":\"array\",\"items\":{\"$ref\":\"#/$defs/n\"},\"minItems\":0},"
    + "{\"type\":\"array\",\"items\":{\"$ref\":\"#/$defs/n\"},\"maxItems\":99}]}}}";

String instance = "[".repeat(d) + "\"x\"" + "]".repeat(d);   // [[[["x"]]]]

SchemaRegistry registry = SchemaRegistry.withDefaultDialect(SpecificationVersion.DRAFT_2020_12);
Schema s = registry.getSchema(schema);
s.validate(instance, InputFormat.JSON);

depth  instance   validate     errors
19     41 B       354 ms       1,048,576
20     43 B       694 ms       2,097,152
21     45 B       5,746 ms     4,194,304
22     47 B       OutOfMemoryError

Both anyOf arms accept an array, so both descend into the same child, twice per parent all the way
down. jstack mid-run is just AnyOfValidator / Schema.validate / RefValidator / ItemsValidator
repeating, RUNNABLE. getSchema is flat at 0 ms; it's all in validate.

A level costs 2 bytes, so more heap buys 2 characters per doubling.

Affected versions

Same schema and instance, -Xmx2g:

depth  instance  DEFAULT        BOOLEAN        FLAG           failFast+BOOLEAN
20     43 B      857 ms         972 ms         615 ms         697 ms
21     45 B      5961 ms        6492 ms        6156 ms        5706 ms
22     47 B      OutOfMemoryError (all four)

depth  instance   validate      errors
14        250 B        365 ms    1,179,613
15        267 B        769 ms    2,359,261
16        284 B    OutOfMemoryError

Start with the supplied Java reproducer and profile the repeated stack through AnyOfValidator, Schema.validate, RefValidator, and ItemsValidator; getSchema is not implicated. Compare validation behavior and allocations at increasing depths, then verify that equivalent recursive paths no longer cause exponential cost or OutOfMemoryError while validation results remain correct.