compat!: Deprecate the streamz interface in holoviews.streams

[hoxbro]

The streaming notebook has been ignored for some time, and the author of streamz has mostly retired it:

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 88.79%. Comparing base (7b2161e) to head (b5f13a2).

Files with missing lines	Patch %	Lines
holoviews/streams.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6490      +/-   ##
==========================================
- Coverage   88.79%   88.79%   -0.01%     
==========================================
  Files         323      323              
  Lines       68955    68958       +3     
==========================================
+ Hits        61229    61230       +1     
- Misses       7726     7728       +2     

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[maximlt]

Can some explanation be provided to the PR text on Github?

[maximlt]

To expand a little bit:

The streaming notebook has been ignored for some time

This means the notebook was no longer tested on the CI.

the author of streamz has mostly retired it

This links to a Google Doc where Martin Durant, streamz's author, provides a list of all his OSS contributions/projects with their status.

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streamz has about 20k downloads/month. Not super low but indeed much lower than some other projects Martin takes care of (e.g. fsspec).

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This means hvplot.streamz also has to be deprecated.