hatch-v1.16.x (#2106)

* Change user-agent to use sys module, prepare docs for release

* release Hatchling v1.28.0

* release Hatch v1.16.0

* Remove unused import

* Fix formatting

* Fix additional formatting

* Fix User Agent Header test and version format

* Fix test format

* Release 1.16.0 - Fix missing changelog entries

* Address review changes

* Update src/hatch/index/core.py

Co-authored-by: Ofek Lev <[email protected]>

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Co-authored-by: Ofek Lev <[email protected]> 8e1a709

Author: cjames23