Updates to work with connection changes

We can't call @raw_connection right away anymore, because it is nil until
it is used after the changes in rails/rails#44576
and rails/rails#44591.

Also we need to have @lock established in order to be able to use
`with_raw_connection`. In the abstract_adapter implementation, that happens
after the arel_visitor is set, but in oracle enhanced, we need to use
`with_raw_connection` to check the database version in order to pick with
visitor to use. Calling lock_thread = nil before super means @lock isi
available to set the arel_visitor.

Rails rails/rails#48229 also requires an internal_exec_query
method that is called by the abstract adpater's exec_query. Naively renaming
the oracle-enhanced's exec_query to internal_exec_query makes the oracle
enhanced tests run.

I also saw errors due to `active?` using @raw_connection. `valid_raw_connection`
ends up calling `active?` via `with_raw_connection` and `verify` so that
can't be used as a replacement for @raw_connection here. Borrowing from
the postgres adapter implementation to get around this.

lib/active_record/connection_adapters/oracle_enhanced/database_statements.rb

@@ -15,7 +15,7 @@ def execute(sql, name = nil, async: false)
           log(sql, name, async: async) { @raw_connection.exec(sql) }
         end
 
-        def exec_query(sql, name = "SQL", binds = [], prepare: false, async: false)
+        def internal_exec_query(sql, name = "SQL", binds = [], prepare: false, async: false)
           sql = transform_query(sql)
 
           type_casted_binds = type_casted_binds(binds)

lib/active_record/connection_adapters/oracle_enhanced_adapter.rb

@@ -247,6 +247,7 @@ def dealloc(stmt)
       end
 
       def initialize(config_or_deprecated_connection, deprecated_logger = nil, deprecated_connection_options = nil, deprecated_config = nil) # :nodoc:
+        self.lock_thread = nil
         super(config_or_deprecated_connection, deprecated_logger, deprecated_connection_options, deprecated_config)
         @enable_dbms_output = false
         @do_not_prefetch_primary_key = {}
@@ -446,7 +447,11 @@ def active? # :nodoc:
         # #active? method is also available, but that simply returns the
         # last known state, which isn't good enough if the connection has
         # gone stale since the last use.
-        @raw_connection.ping
+        @lock.synchronize do
+          return false unless @raw_connection
+          @raw_connection.ping
+        end
+        true
       rescue OracleEnhanced::ConnectionException
         false
       end
@@ -696,7 +701,7 @@ def max_identifier_length
       alias index_name_length max_identifier_length
 
       def get_database_version
-        @raw_connection.database_version
+        valid_raw_connection.database_version
       end
 
       def check_version