ObjectParser should throw XContentParseExceptions, not IAE

[jpountz]

ParsingException is nicer since it includes the place where the parsing error occurred.

[elasticmachine]

Pinging @elastic/es-core-infra

[nik9000]

ParsingException can't move because it extends ElasticsearchException. We made XContentParseException which doesn't extend ElasticsearchException to use directly from the xcontent stuff. I think the tests should catch either or something should wrap somewhere.

[dakrone]

I agree with @nik9000, this should use XContentParseException so that it can keep being decoupled from ElasticsearchException

[jpountz]

This sounds good to me. I updated the title and description of the issue.