Make `CreateTable.location` / `AlterTable.location` make more sense

`CreateTable.location` has no documentation and is a tricky edge case, not always set even when SQL statement did set location.

https://docs.rs/sqlparser/latest/sqlparser/ast/struct.CreateTable.html#structfield.location

Since this took some time to figure out, here's what I've found for others also pondering its role:

- `CREATE EXTERNAL TABLE .. LOCATION 'foo'` sets `CreateTable.location`
- `CREATE TABLE .. LOCATION 'foo'` sets `CreateTable.hive_formats.location`
- `ALTER TABLE .. LOCATION` sets `AlterTable.location`
- `AlterTable.location` types are about Hive, and is thus a bit confusing for external tables: https://docs.rs/sqlparser/latest/sqlparser/ast/enum.Statement.html#variant.AlterTable.field.location
- alter vs create behaviors thus do not match

Maybe make Hive syntax use the top-level `location` field?

Comienza con las definiciones de docs.rs para CreateTable.location, CreateTable.hive_formats.location y AlterTable.location; después, sigue el comportamiento del parser para las formas CREATE EXTERNAL TABLE, CREATE TABLE y ALTER TABLE LOCATION enumeradas en el issue. Se considera terminado cuando la semántica de location sea coherente o esté documentada con claridad, y exista cobertura de regresión para esos casos.

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