[columnar] fixes edge case for vacuum udf and adds vacuum_full udf

[JerrySievert]

Two Parts

1. Fixes an edge case on the vacuum UDF where the state of holes can get weird, instead of calculating, just retrieve the state as needed after a change. This is less performant, but more correct.
2. Adds columnar.vacuum_full() UDF that allows for the full vacuum of a schema of columnar tables as a convenience function.

columnar.vacuum_full(schema, sleep_time, stripe_count)

This is a convenience function that allows for a full incremental vacuum to be called to vacuum a full schema incrementally, table by table.

Argument	Type	Description	Default
schema	name	Schema to vacuum, will query for any tables	public
sleep_time	real	Amount of time to wait between each call of the columnar.vacuum UDF in seconds (uses pg_sleep)	0.1
stripe_count	int	Number of stripes to attempt to vacuum between pg_sleep calls	25

Usage

SELECT columnar.vacuum_full();
SELECT columnar.vacuum_full('public', 0.1, 25);
SELECT columnar.vacuum_full(sleep_time => 1.5);

[wuputah]