(note: found via https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=65180)

Looks like overflow checks not being by IonParser can result in one of outcomes:

• an Ion RuntimeException being thrown, when method getIntValue() is called with value beyond 32-bit int range
• quiet truncation of value without failure

Instead, this should be surfaced same as equivalent JsonParseException JSON-backed JsonParser throws in similar situation -- see ParserBase.convertNumberToInt() (and ParserBase.reportOverflowInt()) for examples of handling.

Same probably affects long overflow as well (wrt BigInteger range value)