Retrieve tab key from form attributes even when action is urlencoded

[christianwach]

Overview

Fixes problems associated with Contribution Page forms and Event Management forms as described in this comment by @kcristiano.

The issue has appeared since #13043 because the existing code relied on URLs not being URL-endcoded to tease out the component for the active tab. Please see the discussion on the linked issue for further details.

This PR replaces #13090 and #13089.

Before

The component is misidentified by parsing the action attribute of the form object using basename(), but fails because the q variable is (properly) URL-encoded since #13043.

After

The component is correctly identified by parsing the action attribute of the form object using basename() by not assuming that the URL is in its raw state. The new code URL-decodes the action URL when needed before teasing out the component name.

Comments

This only fails in WordPress because Drupal uses clean URLs by default and WordPress can never use clean URLs in wp-admin because everything is routed through wp-admin/admin.php.

[civibot]

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[kcristiano]

tested on WP with CiviCRM 5.8 beta 1 and Drupal 7 with CiviCRM 5.8 beta1

• (r-explain)Pass
• (r-test) Pass
• (r-code) Pass
• (r-doc) Pass
• (r-maint) Pass
• (r-run) Pass: created Contrib pages on D7 and WP
• (r-user) Pass
  (r-tech)Pass

@eileenmcnaughton @seamuslee001 this Patch works well and has been tested. I believe we should add to 5.8

[seamuslee001]

This looks good to me and given Kevin's testing Merging