EQL: Remove parser handling for functions

[rw-access]

Relates to #51556

Removed the parser handling for all functions, and letting the Verifier handle it. I commented out the array functions in queries-unsupported.eql, because they on longer raise ParsingExceptions, and only VerifierExceptions.

elasticsearch/x-pack/plugin/eql/src/test/java/org/elasticsearch/xpack/eql/parser/GrammarTests.java

Lines 39 to 47 in a462700

	public void testUnsupportedQueries() throws Exception {
	EqlParser parser = new EqlParser();
	List<Tuple<String, Integer>> lines = readQueries("/queries-unsupported.eql");
	for (Tuple<String, Integer> line : lines) {
	String q = line.v1();
	ParsingException pe = expectThrows(
	ParsingException.class,
	"Query not identified as unsupported: " + q,
	() -> parser.createStatement(q));

[costin]

LGTM.

[astefan]

LGTM