laurenz/oracle_fdw ORACLE_FDW_2_4

Enhancements:

Support push-down of uuid values.
Per request from @GaddipatiAsish.
Introduce a server option nchar, turned off by default.
This option, if set, enables the fix for NCHAR and NVARCHAR2 columns introduced in 2.3.0.
We don't want that by default, since it causes a noticable performance hit and makes UPDATEs with long strings fail with ORA-01461.
Problem reports by @threenotrump, @chunter and @philflorent.
Push down LIMIT clauses if possible.
These are pushed down as FETCH FIRST n ROWS ONLY from Oracle 12.2 on.
Based on a patch by @darold, per request from @iliasaz.

Fix a performance regression introduced in 2.3.0 by the fix for NCHAR and NVARCHAR2 columns.
Reported by @philflorent.
Fix a crash with type coerced array parameters.
This can make queries fail with a WHERE condition like
```
WHERE varcharcol = ANY ($1);
```
where $1 is a text[].
Reported by @samuelchoi16.
Fix numeric precision in IMPORT FOREIGN SCHEMA.
In Oracle the precision of a NUMBER can be less than the scale, but that is not allowed in PostgreSQL.
That leads to errors during IMPORT.
Reported by @alberto-dellera.
Translate Oracle NUMBER to boolean correctly.
The documentation says that numbers greater than 0 are mapped to TRUE, but oracle_fdw gagged on numbers greater than 1 with errors like
```
ERROR:  invalid input syntax for type boolean: "2"
```
Reported by @mariszin.
Fix crash during ANALYZE of certain foreign tables.
If the Oracle table has more columns than the foreign table, ANALYZE on the foreign table caused a crash.
Reported by Jan and @SeanKimMel.
Fix build with unset ORACLE_HOME and Instant Client 21.
Reported by @fjf2002.
Use the correct user mapping in SECURITY DEFINER contexts.
Before this, oracle_fdw always used the current user to determine the security context, which is wrong if a foreign table was accessed in a SECURITY DEFINER function.
Reported by @ksmalara.