Provide better description wording for the Diff settings UI

Problem/Motivation

From #2810871: Explain fields configuration and private discussion with @miro_dietiker, we still need to improve some wording for the Diff settings UI.
Text/UI wording is never easy to define, thus we need to discuss properly to give to the user better/short/clean/concise descriptions.

From the parent issue (comment #21):
1.

Yeah, these "per category settings details-wrappings" could be easier for the end user/self-explaining, but then for the visual_inline_theme aren't the label "VISUAL INLINE LAYOUT SETTINGS" and the description "Theme used for Visual inline layout when comparing revisions." too much/repetitive ?
Not sure, but imo, if we would keep it like this, I'd suggest removing the description (or at least saying something more "useful", like the Leading/Trailing examples ?)

2.

About "Leading context lines", "Trailing context lines" and their descriptions, not sure which better wording we can use to not repeat things. Maybe just "Leading" and "Trailing" as select labels and keep the descriptions (?)

3.

More:

+++ b/diff.module
@@ -78,11 +78,14 @@ function diff_help($route_name, RouteMatchInterface $route_match) {
+      return '<p>' . t('This table provides a summary of the field support found on the system. For every field a diff plugin can be selected and configured. This settings are applied to Unified and Split fields layouts.') . '</p>';

As you said once "We want to avoid the diff word in the UI" (comment #15.2), how can we change this "For every field, a diff plugin can be selected and configured." ?

Also imo this new help text is too long, but if it is fine, then: "This" --> "These".

+++ b/src/Form/GeneralSettingsForm.php
@@ -98,11 +82,12 @@ class GeneralSettingsForm extends ConfigFormBase {
+

Unnecessary new line.

+++ b/src/Plugin/diff/Layout/VisualInlineDiffLayout.php
@@ -25,6 +25,7 @@ use Symfony\Component\HttpFoundation\RequestStack;
+ *   description = @Translation("Visual layout, revision comparison is made as the content is rendered for the user."),

Not sure what you mean by "made as the content is rendered for the user".

Private chat:

[...]
the (visual inline) plugin triggers an entity view / rendering.
instead of field based view / rendering / value comparision.
The user usually doesn't know the term rendering though.
Dunno, it's an admin screen, so we might be fine to use those terms.

It might be healthy to do it there. We found the word "Visual inline" for the end user, but in the plugin description, it's the time to explain what it means..

I was even thinking about removing "Inline" from the plugin label because "Visual" might be clear enough.

Proposed resolution

- discuss about the best wording to display to the end user/site builder
- upload the patch
- review

Remaining tasks

User interface changes

Improved some wording in /admin/config/content/diff/general and /admin/config/content/diff/fields

Before:

After:

API changes

Data model changes