Adds OnStart/OnStop lifecycle Annotations

[jasonmills]

This provides two new annotations, OnStart and OnStop. Each will append their respective hooks into the application Lifecycle when the provided option function is executed.

Usage:

type Interface interface {
    Start(context.Context) error
    Stop(context.Context) error
}

func New() (Interface, error)

var Module = fx.Provide(fx.Annotate(
    New,
    fx.OnStart(func(ctx context.Context, server Interface) error {
      return server.Start(ctx)
    }),
    fx.OnStop(func(ctx context.Context, server Interface) error {
       return server.Stop(ctx)
   }),
))   

Which is functionally equivalent to:

var Module = fx.Provide(
  func(lifecycle fx.Lifecycle) (Interface, error) {
    server, err := New()
    lifecycle.Append(fx.Hook{
      OnStart: func(ctx context.Context) error { return server.Start(ctx) }, 
      OnStop: func(ctx context.Context) error { return server.Stop(ctx) },
    }
    return server, err
  },
)  

Note for reviewers:

• The underlying implementation is unified for each hook type and may be easily extended should additional hook fields be added to the Hook type.
• This slightly modifies the parameter implementation of the private annotation type, this was required in order to make the hook annotation types able to detect when a given annotated function provides a required hook (closure) parameter. Without this any hook that takes a dependency on a type that is constructed in the same annotation would trigger a circular dependency.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #895 (67de07f) into master (4f51a19) will increase coverage by 0.18%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #895      +/-   ##
==========================================
+ Coverage   98.53%   98.71%   +0.18%     
==========================================
  Files          30       30              
  Lines        1163     1328     +165     
==========================================
+ Hits         1146     1311     +165     
  Misses         11       11              
  Partials        6        6              

Impacted Files	Coverage Δ
annotated.go	99.69% <100.00%> (+0.30%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us.

[sywhang]

Good start. Left some comments.

Also, there a couple of missing test cases that would be nice to cover here:

• Providing nested hooks and validating the execution order
• fx.Invoke can also take in an fx.Annotated function. I don't think you'll need much (if any) modifications to the existing code, but can you add a test case for that?

[sywhang]

also it looks like this branch is out-of-date with the master branch - can you rebase on master?

[sywhang]

👏 Coming together nicely - left one more round of reviews, mainly around cleanliness and readability.

Also try to edit the PR message here to include a brief description of the API and how one might go about using this, since a lot of people come across the PRs as part of the documentation (which we do lack but that's a separate story).