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

Empieza en el lexer y el parser revisando el manejo de los tokens que comienzan con `$`, especialmente la ruta que actualmente produce `Token::Placeholder`, y revisa el manejo del dialecto Snowflake. El trabajo estará terminado cuando las formas de columnas documentadas de staged-file y COPY INTO se analicen correctamente sin introducir regresiones en la sintaxis existente de placeholders.

Escrito por el modelo de indexación a partir del texto del issue.