snowflake column identifier for copy into / query data staged in files

According to documentation, Snowflake allows:
* [query data staged in files](https://docs.snowflake.com/en/user-guide/querying-stage.html#required-parameters) with an identifier of a form `[.]$[.]`
* [copy into table](https://docs.snowflake.com/en/user-guide/data-load-transform.html) with an column identifier containing `$` character like `select t.$1,t.$2,t.$3 from @~/datafile.csv.gz t;`

Although the feature seems to be snowflake specific, it cannot be implemented within snowflake dialect. It's because tokens starting with `$` character are tokenized into `Token::Placeholder`. That's why parser's change is required.

Initial OpenLineage project issue: https://github.com/OpenLineage/OpenLineage/issues/814

Comece no lexer e no parser revisando o tratamento de tokens que começam com `$`, especialmente o caminho que atualmente produz `Token::Placeholder`, e revise o tratamento do dialeto Snowflake. O trabalho estará concluído quando as formas de coluna documentadas de staged-file e COPY INTO forem analisadas corretamente sem causar regressões na sintaxe existente de placeholders.

Escrita pelo modelo de indexação a partir do texto da issue.