Add intercept on decorator

[idiotsky]

Add support for register service with Interceptor and multiple decorator, apply Interceptor to the outermost decorator,

[tillig]

A description on the PR here, possibly explaining it and linking back to the source issue, would be good. That way in a year from now when we come back and look to see what the point of the PR was (say, during supporting an issue) we have that to reference.

(Update the actual PR description; don't respond with the description here as a comment. Thanks!)

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 88.46154% with 9 lines in your changes missing coverage. Please review.

Project coverage is 90.64%. Comparing base (2115f37) to head (c9f414e).

Files with missing lines	Patch %	Lines
src/Autofac.Extras.DynamicProxy/ProxyHelpers.cs	88.23%	3 Missing and 3 partials :warning:
.../Autofac.Extras.DynamicProxy/DelegateMiddleware.cs	66.66%	1 Missing and 2 partials :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #55      +/-   ##
===========================================
- Coverage    93.44%   90.64%   -2.80%     
===========================================
  Files            1        4       +3     
  Lines          122      139      +17     
  Branches        22       25       +3     
===========================================
+ Hits           114      126      +12     
- Misses           4        6       +2     
- Partials         4        7       +3     

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[tillig]

From what I gather, this PR needs to go through first to help this one. I probably won't look at this one until that one is done.