[META] Port 7.x commits to 8.x

Problem/Motivation

8.x-1.x branched of 7,x-1.x a while ago. We have to make sure that all bugs/changes form 7.x-1.x are in 8.x-1.x. The last common ancestor is 67729a2. Here is a list of all commits since 8.x-1.x branched off.

To do list

- #2343689: D7: Multiple forms submit/cancel closes all child forms
- #2206197: Nested Inline Entity form, issues on node creation with duplication of nested items

WIP

Done

- #1590146: Clone referenced entities
- #2612720: Forward port submission improvements (#ief_element_submit) to D8
- #2187103: inline_entity_form_form_alter() incorrectly combines form level and button level submit handlers
- #2056139: Add option in setting to "Prevent adding a new entity".
- #2174995: commerce_product_line_item_populate() not called for product line item types
- #2170965: WSOD when Views is not enabled
- #2165113: Undefined index: #submit at inline_entity_form_form_alter()
- #2186553: Insignificant typo in inline_entity_form.api.php causes error
- #2074127: Unknown fields added via inline_entity_form_table_fields
- #2324901: Add callback field type for theme_inline_entity_form_entity_table
- #1876652: Weight delta only supports ordering of 50 items
- #2218887: missing documentation in hook_inline_entity_form_table_fields_alter()
- #2185061: Make sanitizing entity property output in the IEF table optional

Proposed resolution

Remaining tasks

User interface changes

API changes

Original issue summary

* 887eec8 - (drupal/7.x-1.x) Issue #2056139 by joelpittet, svenssson: Add option in setting to "Prevent adding a new entity" (7 weeks ago)
* 566f641 - Issue #1876652 by fearlsgroove, criz: Weight delta only supports ordering of 50 items (7 weeks ago)
* 47ffa63 - Issue #2218887 by joachim: Fixed missing documentation in hook_inline_entity_form_table_fields_alter(). (6 months ago)
* 93efa62 - Issue #2343689 by fearlsgroove: Fixed Multiple forms submit/cancel closes all child forms. (6 months ago)
* 7895c2a - Issue #2206197 by adolfo.mansilla | jnicola: Fixed Nested Inline Entity form, issues on node creation with duplication of nested items. (6 months ago)
* 7b5e448 - Issue #2324901 by yannickoo, axe312, marcusx: Added callback field type for theme_inline_entity_form_entity_table. (6 months ago)
* 8229859 - Issue #2223005 by rszrama: Inline_entity_form_cleanup_entity_form_state() doesn't check for an instance's presence in an entity form. (1 year, 1 month ago)
* 3e93c85 - Issue #2185061: Make sanitizing entity property output in the IEF table optional (1 year, 2 months ago)
* d4c7af0 - Issue #2186553 by sender: Fix typo in inline_entity_form.api.php (1 year, 2 months ago)
* 37959cc - (tag: 7.x-1.5) Issue #2074127: Prevent error when the IEF table is trying to show a field not found on the entity. (1 year, 3 months ago)
* 163d478 - Clean up inline_entity_form_form_alter(), fix issues with some forms being submitted twice. (1 year, 3 months ago)
* 524cdbb - Issue #2174995: commerce_product_line_item_populate() not called for product line item types. (1 year, 3 months ago)
* 1a65c1f - Improve inline_entity_form_field_widget_properties_alter(), avoid calling module_exists() for non-IEF widgets. (1 year, 3 months ago)
* d189bcc - Issue #2173539 by fearlsgroove: Views Bulk Operation (VBO) modify entity values broken again. (1 year, 3 months ago)
* d4192bc - Issue #2170965 by jgullstr, bojanz: Prevent WSOD when Views is not enabled. (1 year, 3 months ago)
* a2158c2 - Issue #2165113 by andyg5000: Undefined index: #submit at inline_entity_form_form_alter(). (1 year, 3 months ago)