wrap malformed json number decode in JsonException

[netliomax25-code]

1. A value that starts with a digit or minus enters number decoding, but a malformed exponent or a lone sign/point such as 1e, 1e+, 1E, or -. is only rejected when the collected token reaches new BigDecimal(...).
2. The INDEX_OVERLAY and LAX overlay parsers already wrap that NumberFormatException in a JsonException (NumberValue.bigDecimalValue), but the default CHAR_BUFFER parser (CharScanner.parseJsonNumber) and the CHARACTER_SOURCE parser (JsonParserUsingCharacterSource.decodeNumber) let it propagate unwrapped, so an application guarding untrusted JSON with catch (JsonException) sees a raw NumberFormatException instead.
3. Wrapped the numeric construction at both sites so malformed numbers surface as JsonException, matching the overlay parsers. Added a regression test that checks all four parser types.

[paulk-asert]

Thanks! Merged as part of PR#2715 (GROOVY-12168) including tweaks to fix the build breakage and some consistency improvements.