Package erb: Information

- backport 3.1.4-alt4.3 changes:
  + E2K: add platform patch (ilyakurdyukov@)
  + add BR: /proc to fix build on %e2k
  + gem subpackage (inter)dep fixup
  + minor spec cleanup (see also ALT#46206)
    - sans P: rubygems (still in need)

- + allow access to gem cache for ruby group instead of rvm (closes #48325)
- + added %ruby_gemsplugindir and %ruby_gemplugin macros
- * rearranged load path (closes #48249)
- * changed names for doc packages: ri is doc, html is doc-html (closes #36294)

- - removed ri from %_bindir leaving it in %ruby_bindir