feat: simplify mason hooks on dev and prod server bricks

[renancaraujo]

Description

The internal bricks for webserver code generation (dev_server and prod_server) have fairly complex hooks.

Assuming that after #474 these bricks will be ported to dart_frog_gen, its hooks won't be able to depend on it, making it necessary to execute whatever runs on those hooks directly on our tooling.

Requirements

• Has to happen after or within spike: investigate ways to support packages which hook into the codegen step #474
• Move pregen and post gen logic to dart_frog_gen