Move receiver builder into internal service

[dmathieu]

Description

This moves the receiver builder out of the receiver package, and into service/internal/builders.
There's no real reason for this struct to be public (folks shouldn't call it), and making it private will allow us to add profiling support to it.

Link to tracking issue

#10375 (review)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.68%. Comparing base (6764622) to head (b05f08a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10781      +/-   ##
==========================================
+ Coverage   91.66%   91.68%   +0.02%     
==========================================
  Files         405      406       +1     
  Lines       18979    19032      +53     
==========================================
+ Hits        17397    17450      +53     
  Misses       1223     1223              
  Partials      359      359              

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[dmitryax]

This is a breaking change since it's a different type now

[dmitryax]

I believe we could make it not a breaking change if we make builders.Receiver an alias to receiver.Builder

[dmathieu]

How is that a breaking change?
We're indeed changing it from a struct to an interface, but they match each other, so passing the struct will still work properly.

[mx-psi]

I believe this is not a breaking change, @dmitryax could you show an example where this would break?

[dmitryax]

Imagine if someone extracts the field value and expects a specific type there. That code will break. But that's fine I think. I missed that it's an interface matching the old struct.

[mx-psi]

I believe this is not a breaking change, @dmitryax could you show an example where this would break?