private MatcherSetResult getMatcherSetResult(String matchString) {
        PromQLLexer lexer = new PromQLLexer(
            CharStreams.fromString(matchString));
        lexer.addErrorListener(new ParseErrorListener());
        PromQLParser parser = new PromQLParser(new CommonTokenStream(lexer));
        parser.addErrorListener(new ParseErrorListener());
        ParseTree tree = parser.expression();
        PromQLMatchVisitor visitor = new PromQLMatchVisitor();
        return visitor.visit(tree);
    }
OAP adopt time step by start/end,
reserve step/timeout param to keep consistent with API protocol.
oap-server/server-query-plugin/promql-plugin/src/main/java/org/apache/skywalking/oap/query/promql/handler/PromQLApiHandler.java