Match MySQL's handling of nested subroutine definitions.

A "subroutine" refers to any statement or block of statements that is defined but may not be immediately executed. MySQL has six types of subroutines:

- `CREATE PROCEDURE`
- `CREATE FUNCTION`
- `CREATE TRIGGER`
- `CREATE EVENT`
- `CREATE TABLE AS`
- `CREATE VIEW AS`

Dolt has all of these except functions.

Nesting these constructs is allowed in some cases but not others. Prior to fixing https://github.com/dolthub/dolt/issues/8028, attempting to nest these constructs caused a panic. Now, while there is no panic, our behavior does not necessarily match MySQL

- In cases where both Dolt and MySQL return an error, Dolt's error message should match MySQL.

- In cases where Dolt returns an error but MySQL doesn't, we should match MySQL's behavior.

- In cases where MySQL returns an error but Dolt doesn't, we should either match MySQL, or add additional tests to verify that our behavior is sensible.

Start by reproducing the nested CREATE PROCEDURE, CREATE TRIGGER, CREATE EVENT, CREATE TABLE AS, and CREATE VIEW AS cases in Dolt and MySQL, comparing errors and successful behavior. Done means Dolt matches MySQL where possible, with tests documenting any intentional differences.

Written by the indexing model from the issue text.