CREATE DATABASE statements should not create databases hierarchicaly

[bheni]

If you create a new directory and run dolt sql-server within it, and then connect to it and run:

CREATE DATABASE `db`;
CREATE DATABASE `db/subdb`;

you will end up with the directories:

./db
./db/.dolt
./db/subdb
./db/subdb/.dolt

This breaks backups and causes other problems. We should either not allow / in database names, or create our directories using some filesystem safe encoding (Such as ./db%2Fsubdb)... But I imagine it's probably easiest to prevent slashes in db names.

Repro Steps: Create a new directory to test from and run dolt sql-server

~/datasets/dolt>mkdir hierarchical
~/datasets/dolt>cd hierarchical
~/datasets/dolt/hierarchical>dolt sql-server -H0.0.0.0 -udolt

Connect to the running server and run the queries

~>mysql -h127.0.0.1 -udolt
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 8.0.33 Dolt

Copyright (c) 2000, 2024, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
+--------------------+
2 rows in set (0.00 sec)

mysql> CREATE DATABASE db;
Query OK, 1 row affected (0.08 sec)

mysql> CREATE DATABASE `db/subdb`;
Query OK, 1 row affected (0.10 sec)

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| db                 |
| db/subdb           |
| information_schema |
| mysql              |
+--------------------+
4 rows in set (0.01 sec)

mysql> exit

Check the folders created:

~/datasets/dolt/hierarchical>ls -la
total 0
drwxr-xr-x   4 brian  staff   128 Jul 16 14:24 .
drwxr-xr-x  36 brian  staff  1152 Jul 16 14:13 ..
drwxr-xr-x   2 brian  staff    64 Jul 16 14:24 .dolt
drwxr-xr-x   4 brian  staff   128 Jul 16 14:24 db
~/datasets/dolt/hierarchical>cd db
~/datasets/dolt/hierarchical/db>ls -la
total 0
drwxr-xr-x  4 brian  staff  128 Jul 16 14:24 .
drwxr-xr-x  4 brian  staff  128 Jul 16 14:24 ..
drwxr-xr-x  6 brian  staff  192 Jul 16 14:24 .dolt
drwxr-xr-x  3 brian  staff   96 Jul 16 14:24 subdb
~/datasets/dolt/hierarchical/db>cd subdb
~/datasets/dolt/hierarchical/db/subdb>ls -la
total 0
drwxr-xr-x  3 brian  staff   96 Jul 16 14:24 .
drwxr-xr-x  4 brian  staff  128 Jul 16 14:24 ..
drwxr-xr-x  6 brian  staff  192 Jul 16 14:24 .dolt