Field alter text is translatable but it's a Twig inline template

Problem/Motivation

The type of views_field.mapping.alter.mapping.text is text and text is translatable. The value is a Twig inline template and is passed to Twig engine, see PluginBase::viewsTokenReplace(). But Twig has its own way to translate strings inside a template by using the t/trans filter and such a template should not be translatable.

If the view was shipped as module config, Locale will expose it in the translation UI. Other modules will send such strings to automated translation and would break the view on other languages.

Steps to reproduce

See the MR's test.

Proposed resolution

Set the schema from text to string

Remaining tasks

Decide how to handle the potential BC break: e.g., existing views set static text there, expecting to be translated

User interface changes

Introduced terminology

N/A

API changes

None.

Data model changes

Release notes snippet