Additional BigQuery staged data check for data larger than 100MB

[nj1973]

Tested with an Oracle CLOB value larger than 100MB. Offload fails with:

Load staged data
Fri Dec  8 14:42:57 2023
BigQuery SQL: INSERT INTO `project-01.owner.tab_clob`
SELECT `ID` AS `ID`
,      `DATA` AS `DATA`
,      PARSE_DATETIME('%F %H:%M:%E*S', `LOAD_DATE`) AS `LOAD_DATE`
FROM   `project-01.owner_load.tab_clob`
Step time: 0:00:15
Unhandled exception in offload_table(): 400 Cannot query rows larger than 100MB limit.

We should add a LENGTH check to the Validate staged data step for any BLOB/CLOB columns.

DBA_TABLES.AVG_ROW_LEN does not reflect out of row LOB space used which makes it tricky for us to warn the user at the start of an Offload.