CI Pipeline Compatibility

[TravisCalder]

What did you implement:

• Add "strictMode" functionality
  • "strictMode" is on by default
  • When enabled, an error is thrown when no Rust builds are found
  • When disabled, the error is suppressed
  • "strictMode" can be disabled with custom.rust.strictMode: false
• Fix validation warning
  • serverless does not accept "rust" as a runtime
  • a function can be marked as "rust" the old way, or by adding tags.language: "rust"
• Support predefined artifacts and skip recompile
  • This allows an artifact to be built in one CI-step and deployed in another
  • When artifact is defined, the artifact zip is uploaded and compile is skipped

Closes: #123

How did you verify your change:

Change was verified locally using npm link locally. The following scenarios were verified:

• custom.rust.strictMode set to false, provider changed to provided.al2
  • This resulted in no builds, since no rust functions were found, but no errors
• Set top-level provider.runtime to provided.al2 and added tags: language: "rust"
  • This resulted in the Rust function being correctly identified and compiled
• Added param:artifact as per linked issue
  • When built with serverless deploy --stage stage, compile occurred as per usual
  • When built with serverless deploy --stage stage --param="artifact=path/file.zip" build was skipped and provided artifact was deployed