Add declarative config support for view unit

[jack-berg]

https://github.com/open-telemetry/opentelemetry-configuration/blob/main/schema-docs.md#viewselector-

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.10%. Comparing base (7a46bc5) to head (aeebb99).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #7942   +/-   ##
=========================================
  Coverage     90.10%   90.10%           
- Complexity     7439     7440    +1     
=========================================
  Files           834      834           
  Lines         22546    22548    +2     
  Branches       2236     2237    +1     
=========================================
+ Hits          20316    20318    +2     
  Misses         1531     1531           
  Partials        699      699           

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[jkwatson]

Thanks!