Remove deprecated callback hooks

[awaelchli]

What does this PR do?

Removes deprecated API.
Converted all deprecation warnings to errors.

Per recent decision, we will extend our deprecation window in the following way:

• Deprecate API in v1.x with a warning for removal in v1.(x+2)
• Remove API in v1.(x+2) and convert warnings to errors
• Remove errors for removed APIs in v2.0

Closes #14841
Part of #15049

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Did you have fun?

I made sure I had fun coding 🙃

cc @Borda @awaelchli @ananthsub @rohitgr7 @justusschock @carmocca @ninginthecloud

[carmocca]

Finished up the removal. Didn't run tests though

[awaelchli]

@lantiga I created this issue that summarizes the new plan we discussed offline #15049. PR #14835 would be the first to implement this pattern and then we follow with this one here. Further PRs will then bring back partially what was removed here: #14841

[codecov]

Codecov Report

Merging #14834 (7635128) into master (c04e1cd) will increase coverage by 1%.
The diff coverage is 94%.

❗ Current head 7635128 differs from pull request most recent head 498e981. Consider uploading reports for the commit 498e981 to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #14834     +/-   ##
=========================================
+ Coverage      83%      84%     +1%     
=========================================
  Files         400      329     -71     
  Lines       29501    25856   -3645     
=========================================
- Hits        24432    21763   -2669     
+ Misses       5069     4093    -976