feat(icons): add deprecationReason and alias deprecation feature (#1960)

* feat(icons): add deprecationReason and alias deprecation feature

* chore(tools): run prettier. again.

* fix(scripts): overall alias as object support

* fix(icon.schema.json): add dependentRequired on deprecated properties

* fix(icon.schema.json): remove unicode for now

* fix(icon.schema.json): use const true for deprecated

* fix(build): convert deprecation reason to enum

* fix(build): fix linting of icon.schema.json

* fix(build): renamed gracePeriod => toBeRemovedInVersion

* fix(build): fix aliases map in related icons generation

* fix(build): deprecate aliases using numbers

* feat(icon-schema): separate deprecation reason enumerations, extract removal notice

* fix(icon-schema): fix linting

* Update tools/build-icons/utils/deprecationReasonTemplate.mjs

* fix(icons): add deprecation reason to some more icons

* fix(docs): fix linting issue

---------

Co-authored-by: Karsa <karsa@sztaki.hu>
Co-authored-by: Jakob Guddas <github@jguddas.de>

icons/github.json

@@ -1,6 +1,8 @@
 {
   "$schema": "../icon.schema.json",
   "deprecated": true,
+  "deprecationReason": "icon.brand",
+  "toBeRemovedInVersion": "v1.0",
   "contributors": [
     "colebemis",
     "csandman",