Revert "Issue #1331486 by katbailey, chx, sun, beejeebus, amateescu: Move module_invoke_*() and friends to an Extensions class. Broke core tests after commit."

This reverts commit c80c3e18.

Issue #1331486 by katbailey, chx, sun, beejeebus, amateescu: Move module_invoke_*() and friends to an Extensions class.

Issue #1856178 by swentel, sun, ry5n: '#group' Form API property only works with <details> elements.

Issue #1871696 by tim.plunkett, xjm, sun, msonnabaum, EclipseGc: Convert block instances to configuration entities to resolve architectural issues.

Issue #1839078 by dasjo, tim.plunkett, fago: Implement the new entity field API for the email field type.

Issue #1144716 by Dave Reid, sun: Allow vertical tabs elements to have #title and #description values.

Issue #1812724 by steveoliver, sun: Change notice: Consolidate all form element templates and add theme_hook_suggestons().

Issue #1880378 by swentel, EclipseGc: Fixed Autocomplete broken to search blocks - also triggers notice after clicking 'Next'.

Issue #200344 by Pancho, pillarsdotnet, pdrake, sun: Remove user_module_invoke() and rename user_login_block() to user_login_block_form().

Issue #1535868 by EclipseGc, tim.plunkett, xjm, Jody Lynn, sdboyer, naxoc, tizzo, effulgentsia, dawehner, disasm, beejeebus: Convert all blocks into plugins.

Issue #80855 by sun, vangorra, dman, Damien Tournoud, kkaefer: Add element #type table and merge tableselect/tabledrag into it.

Issue #1825044 by sun: turn contact form submissions into full-blown Contact Message entities, without storage.

Issue #1029460 by sun: Find a better hook than hook_init() for drupal_add_js() and drupal_add_css().

Issue #1571632 by cosmicdreams, marcingy, justafish, chx, KarenS, aspilicious, disasm, swentel, dawehner, rvilar: Convert regional settings to configuration system.

Issue #1168246 by sun, mgifford, Manuel Garcia, mbrett5062, ry5n, Everett Zufelt, nod_, aspilicious, deviantintegral, tim.plunkett: Freedom For Fieldsets! Long Live The DETAILS.

Issue #1667742 by larowlan, nod_, effulgentsia, jessebeach, sun: Change notice: Add abstracted dialog to core (resolves accessibility bug).

Issue #1238484 by mrfelton, ry5n, aspilicious, Bojhan, Xano, nod_, rootatwc, effulgentsia, chx, sun: Ability to mark the form buttons to be of a specific type (so that they can be styled differently).

Issue #1790280 by nod_, Bojhan, Wim Leers, danillonunes, deviantintegral, Kiphaas7, benjifisher, sun, yoroy, Everett Zufelt, jenlampton, aspilicious: Module page redesign 2.0.

Issue #1137920 by jessebeach, lewisnyman, tkoleary, Bojhan, webchick, benjifisher, nod_, sjbassett, kathryn531, effulgentsia, Everett Zufelt: fixed toolbar on small screen sizes and redesign toolbar for desktop.

Issue #891112 by Berdir, sun, Amitaibu, siharris, Cottser: Replace theme_item_list()'s 'data' items with render elements.

Issue #1790920 by alexpott, japicoder, LinL, heyrocker: Move cron_last(), node_cron_last() and common_test_cron() to state system.

Issue #200344 by Pancho, pillarsdotnet, pdrake: Remove user_module_invoke() and rename user_login_block() to user_login_block_form().

Issue #1808200 by sun: Fixed Unit test performance significantly decreased since system list config conversion.

Issue #492720 by pivica, seutje, nod_, JamesAn, sun: Refactor system.js file and use Drupal form states and form ajax.