Update Oracle backend supports_sequence_reset = True

[David Sanders]

The Oracle backend currently specifies supports_sequence_reset = False. It looks as though it's been this way since the flag was added to the Oracle backend since ​https://github.com/django/django/commit/0df4593f0ed.

This commit appears to have been for the 1.5 release [1] which was released in Feb 2013. A few months later Oracle 12.1 [2] was released in July 2013. It's quite hard to determine when ALTER SEQUENCE … RESTART support was introduced but from some pain-staking searching I found that apparently 12.1 included support for it but it wasn't documented until 18c [3]:

There is a new option for altering a sequence that appeared in 12.1 but was not documented until 18c:
alter SEQUENCE [schema_name.]{sequence_name} restart;

[1] ​https://docs.djangoproject.com/en/5.0/releases/1.5/
[2] ​https://en.wikipedia.org/wiki/Oracle_Database#Releases_and_versions
[3] ​https://www.red-gate.com/simple-talk/databases/oracle-databases/oracle-sequences-12c-features-including-identity/

[David Sanders]

Interestingly someone's already added the required sequence reset methods to db.backends.oracle.operations.DatabaseOperations to support flushing: ​https://github.com/django/django/blob/d658a3162fbeb68d148d1b2fcf4da4fe1437eddb/django/db/backends/oracle/operations.py#L526

The Oracle attribute ​DatabaseOperations.__sequence_reset_sql(), which uses a PL/SQL block, appears to have origins way back to 2007 when it was first added as ​_get_sequence_reset_sql()

It looks like that could be simplified to use the ALTER syntax?