Provide a more convenient way to translate texts that are contained in ECA configurations

Problem/Motivation

We have many areas where ECA is rendering or producing some output to end users. For multi-language sites, often times the text to output needs to be somehow translated.

There are a couple of ways how to make texts in ECA translatable. Some of them I can currently think of:

1. Use the "Translate" action
2. Use "Render: Twig" and use the trans filter in there
3. Use Parameters and put translated texts in there, either using Yaml or use its natively supported configuration translation

Option 1 and 2 only run through Interface translation, which requires sometimes an additional manual step to add missing interface translations, e.g. when shipping from test to production.

None of these options are ideally convenient and maybe we can find a better way.

Steps to reproduce

Proposed resolution

One way I could think of is that ECA provides a separate place for collecting and providing a "flat" interface to translate texts, such as the title of a link from a "Render: link" action.

I guess, what doesn't make that much sense, is trying to make the ECA config structure itself translatable. It could influence the logic and that would be outside the scope of translation.

Remaining tasks

User interface changes

API changes

Data model changes