importccl: DELIMITED should match more closely the functionality of mysql's LOAD INTO

[spaskob]

Currently DELIMITED mode for importing text files has limited support for handling unmatched quotes in enclosed fields. Mysql supports a broad range of use cases and since DELIMITED is meant as our analog of Mysql's LOAD INTO command we should get them to par. Also this is currently causing problems with on-boarding enterprise clients. See #40374 which deals with mishandling of a few rows in large csv-like files.

This what one can achieve with MySql today when importing file quotes.csv with separator |:

"Iam"|quoted field.
I"a"m|non-quoted 2 quotes in middle.
"I"a"m"|quoted 2 quotes in middle.
I"am|non-quoted quote in middle.
"I"am"|quoted quote in middle.

Our current implementation crashed on this input, while in MySql this is treated quite sanely:

mysql> LOAD DATA INFILE 'quotes.csv'  into table baz FIELDS TERMINATED BY '|' ENCLOSED BY '"';
Query OK, 5 rows affected (0.03 sec)
Records: 5  Deleted: 0  Skipped: 0  Warnings: 0

mysql> select * from baz;
+-------+--------------------------------+
| s1    | s2                             |
+-------+--------------------------------+
| Iam   | quoted field.                  |
| I"a"m | non-quoted 2 quotes in middle. |
| I"a"m | quoted 2 quotes in middle.     |
| I"am  | non-quoted quote in middle.    |
| I"am  | quoted quote in middle.        |
+-------+--------------------------------+
5 rows in set (0.01 sec)

Describe the solution you'd like
Add support for the above use case in Cockroah DELIMITED import mode.

Additional context
See #40374

[spaskob]

@robert-s-lee @rolandcrosby
Our DELIMITED mode is lacking compared to MySql and this new feature should virtually eliminate csv import problems.