Stats command doesn't work with aggregates with no field argument

[51-code]

Describe the bug

index=abc earliest=-4y | stats avg by host Results in an exception: java.lang.IllegalStateException: failed to parse at line 2:35 due to mismatched input 'avg' expecting {'avg(', 'mean(', 'c(', 'count(', METHOD_AGGREGATE_COUNT, METHOD_AGGREGATE_COUNT_C, 'dc(', 'distinct_count(', 'earliest(', 'earliest_time(', 'estdc(', 'estdc_error(', 'first(', 'last(', 'latest(', 'latest_time(', 'list(', 'max(', 'median(', 'min(', 'mode(', 'p(', 'perc(', 'exactperc(', 'upperperc(', METHOD_AGGREGATE_P_VARIABLE, METHOD_AGGREGATE_PERC_VARIABLE, METHOD_AGGREGATE_EXACTPERC_VARIABLE, METHOD_AGGREGATE_UPPERPERC_VARIABLE, 'percint(', 'range(', 'rate(', 'stdev(', 'stdevp(', 'sum(', 'sumsq(', 'values(', 'var(', 'varp(', 'per_second(', 'per_hour(', 'per_day(', 'per_minute(', 'partitions=', COMMAND_STATS_MODE_ALLNUM, COMMAND_STATS_MODE_DELIM}

Expected behavior

The query should parse. Correct implementation in PTH-10 would result in a table with numerous columns of data for different averages. This should work for any aggregate command (not just avg).

How to reproduce

Run the query.

Screenshots

Software version

5.4.0

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Additional context