First-time CLI builds are really slow

[arctic-hen7]

The first time the CLI builds, it takes a very long time to complete. These are the stages it goes through for perseus serve:

• Build all dependencies and the user's code (long)
• Run static generation (almost instantaneous)
• Build for Wasm (long)
• Organize bundle (very quick)
• Build all server dependencies and the user's code (long)
• Run the server (almost instantaneous)

There are a few infrastructure changes I want to propose to shorten first-time builds (and all further builds for that matter). First, a workspace should be constructed in the preparation stage so that the two subcrates share a target/ directory, which means the server doesn't need to rebuild everything. Second, run the build for static generation and the Wasm build in parallel (which can be done for different targets).

These changes should significantly reduce initial build times, and further reduce later builds, making Perseus even faster in development. By increasing iteration time, we increase develop productivity, meaning people focus more on their own code and less on waiting at their terminals.

• Create workspace at runtime
• Parallelize builds

[arctic-hen7]

Having created a workspace at runtime, it helps a bit. Parallelization will hopefully be much more effective though.

[arctic-hen7]

This is complete, and will be released with v0.2.0!