[V3] Packages Deprecation

[Convly]

What does it do?

As we released Strapi V4 and are about to reach end-of-support for Strapi V3 (around Q3 2022).
We decided to add a deprecation notice to the concerned packages so that users can be warned in advance about what's going to happen.

Packages will either:

• Not going to change at all (no deprecation warning)
• Be moved to another package (deprecation warning + link to the V4 version of the package)
• Be deleted (deprecation warning + notice of no further support)

Why is it needed?

We want to prepare the migration from V3 to V4 the best we can, and it includes warning the community as soon as possible about the changes that are about to come.

How to test it?

Open some packages readme (strapi, strapi-hook-ejs, strapi-plugin-graphql) files and... read them 🤷

[codecov]

Codecov Report

Merging #12520 (dff93d0) into releases/v3.6.9 (13f37e9) will not change coverage.
The diff coverage is n/a.

@@               Coverage Diff                @@
##           releases/v3.6.9   #12520   +/-   ##
================================================
  Coverage            58.12%   58.12%           
================================================
  Files                  185      185           
  Lines                 6431     6431           
  Branches              1396     1396           
================================================
  Hits                  3738     3738           
  Misses                2230     2230           
  Partials               463      463           

Flag	Coverage Δ
front	?
unit	58.12% <ø> (ø)

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[alexandrebodin]

The timing ain't right but the rest is good :)