Deprecations: list of all past and ongoing deprecations

[humitos]

We have been deprecating pretty old non-used or broken features in the last weeks and we found ourselves a little lost about the big picture (whole plan) but also about what are the features that are going through the deprecation time. This issue just list them all here with the exact dates when they are making effective:

Feature	Email (dates)	Removal (dates)	Affected projects
#10514: Drop PyPy support	Not sent	July 18th	0
#10550: Fail builds without index.html	July 19th	August 1st	~114
#10508: Install latest version of requirements	July 10th	August 7th	New projects
#10494: Remove UPDATE_CONDA_STARTUP	Jun 29th	August 28th	13
#10588: Remove DONT_SHALLOW_CLONE	June 26th	August 28th	61
#5609: Doctools without config file	July 11th	August 28th	1.8k
#10562: Remove python.system_packages	August 7th	August 29th	~8k
#10367: No .readthedocs.yaml and v1	Weekly (starting May 31th)	September 25th	All projects
#10584: Drop support for MkDocs 0.17.3	August 2nd	October 3rd	293
#10365: Drop support for Sphinx 1.x	Aug 23th	October 3rd	~8k
#10589: Drop build.image	Weekly	October 16th	~16k
#8840: Drop VCS (svn, hg, bzr)	March 20th	June 3rd	~6k
#11206: Drop MKDOCS_THEME_RTD feature flag	Undefined	April 15th	~2
#9993: Don't serve README.html at /	May 28th	July 1st	~250
#11441: Don't auto-inject Sphinx context/configs	Soon	July 29th & Oct 7th	All Sphinx projects
#9530: Auto-injection of Google Analytics	Undefined	Oct 7th	~5k
#8659: Deprecate setup.py install	Undefined	Undefined	~350
#10677: Embed APIv2 removal		Jan 20th	~30
#10637: Stop finding conf.py and mkdocs.yml	Undefined	January 20	~950
#11037: Old incoming webhooks	Undefined	Undefined	N/A
#11839: APIv2	Undefined	Undefined	N/A

Related: #9779

Note: the table is sort by ascending "Removal (dates)"

[ericholscher]

This looks good. I might align the Sphinx 1.8 & Mkdocs .17 dates, since they seem like basically the same deprecation (eg. removing old default build tools).