JSON converter caches: field-type-blind cache key, dead sealed-subtype registration for containers, unbounded kotlinx cache

[zantvoort]

• JsonORMConverterImpl's CacheKey omits the field type (storm-jackson2/src/main/java/st/orm/jackson/spi/JsonORMConverterImpl.java:65-68) while custom serializers are registered per field type (:111-113). Two @Json fields sharing a @JsonSerialize(using = S) therefore share one cached mapper, and the second field's serializer is silently bypassed.
• getRawType returns List.class for @Json List<Shape> (:76-78 with :133-141), so sealed-subtype registration is dead for container-typed fields.
• kotlinx: JSON_CACHE is an unbounded ConcurrentHashMap keyed on a component that buildJson never reads (storm-kotlinx-serialization/src/main/kotlin/st/orm/serialization/spi/JsonORMConverterImpl.kt:48, 51-54).

Same fixes apply to jackson3 (identical line numbers).