[#8489] Add compound index to modTemplateVarResource

[ReUp][#8489] add a new index in the site_tmplvar_contentvalues table

(cherry picked from commit d90c233abd2f10e279cc613d33e2e38f9bf4a475)
[#9672] Fix invalid ini_get call in modDbRegister
Make caching aliasMap optional to reduce memory usage

Disabling this will allow contexts with a large number of Resources to use less memory and gain performance. Smaller sites will perform better with this enabled.
Merge branch 'release-2.2' into develop

* release-2.2:
  Make caching aliasMap optional to reduce memory usage
  [#9672] Fix invalid ini_get call in modDbRegister
  [#8489] Add compound index to modTemplateVarResource

Conflicts:
	core/docs/changelog.txt