Allow to specify zenstack generate output folder in repl CLI

[platon-ivanov]

Is your feature request related to a problem? Please describe.

The repl command allows us to provide a --prisma-client option. However, when I do, I get:

An unexpected error occurred:
 Error: Generated "enhance" function not found. Please run `zenstack generate` first.

I did run zenstack generate from the root of the project and pointed to the prisma generate output folder. The problem is that I also have a custom zenstack generate output folder, so repl wouldn't detect it automatically.

Describe the solution you'd like
--schema option to specify a custom location to load ZenStack generated modules.