Ensure schema exists when creating migrations table

[B4nan]

Describe the bug
When using custom schema name in postgres, migrator tries to create the migrations table without ensuring the target schema exists.

To Reproduce
Steps to reproduce the behavior:

1. specify custom schema
2. try to use migrations when the schema does not exist yet
3. profit

Expected behavior
Schema should be created/ensured before we try to create the migrations table.

Versions

Dependency	Version
node	16.10
mikro-orm	5.1.2
postgres	5.1.2

[carlswann]

When is this fix going to be published?

[B4nan]

Every commit is published to npm.