Add support for Snowflake identifier function

[yoavcloud]

Expand the support for the IDENTIFIER function in Snowflake, which is used to generate identifiers dynamically. See here: https://docs.snowflake.com/en/sql-reference/identifier-literal

The ObjectNamePart enum was extended with a new part type to support the use of the identifier function as an object name. Some work went into organizing Parser:parse_object_name a bit.

A few examples:

-- identifier for table name
create or replace temp table identifier('test')(c1 int, identifier int); 
-- identifier for column name
select identifier('identifier') from test;
-- identifier for table name
select c1 from identifier('test');
-- identifier for table alias
select identifier('alias1').* from test as alias1;