Add Support for Transient Name Server (TNS)

[TriangleBoy]

Adding a new Module to support the TNS (Transient Name Server) API.

TNS has three APIs that allow for data retrieval, one that allows you to search for an object name based on certain criteria, one that allows you to get data bout an object given its name, and one that allows you retrieve specific files based on a URL.

This addition will expose the first two APIs.

[codecov]

Codecov Report

❌ Patch coverage is 57.14286% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.06%. Comparing base (6a3c231) to head (0b62079).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
astroquery/tns/core.py	40.00%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3571      +/-   ##
==========================================
- Coverage   73.09%   73.06%   -0.03%     
==========================================
  Files         219      221       +2     
  Lines       20592    20627      +35     
==========================================
+ Hits        15052    15072      +20     
- Misses       5540     5555      +15     

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