Condionally limit total rows in COPY FROM

[waynexia]

What problem does the new feature solve?

Follow up of #3819

After #3819, a COPY FROM can only copy a hardcoded number of rows, and terminate the COPY FROM task without any hint.

What does the feature do?

Change the limit behavior to

• do not limit by default
• make the limit rows configurable

As for the way to config it, we come up with two possible approaches:

• Add a LIMIT segment in COPY FROM statement, like

COPY [<db>.]<table_name>
FROM { '<path>/[<filename>]' }
[ [ WITH ]
 (
   [ FORMAT =  { parquet } ]
   [ PATTERN = '<regex_pattern>' ]
 )
]
[LIMIT NUM]

• Add an option for it:

COPY [<db>.]<table_name>
FROM { '<path>/[<filename>]' }
[ [ WITH ]
 (
   [ FORMAT =  { parquet } ]
   [ PATTERN = '<regex_pattern>' ]
   [ LIMIT = NUM ]
 )
]

We would personally prefer the first way as it is more natural to write.

Implementation challenges

No response