Make invalid reference label field formatter setting translatable [#3526262]

Problem/Motivation

In the config schema of the reference_value_formatter the invalid_reference_label is specificed as being a string, thus the value is not translatable using config translation, although it most likely differs per language.

Steps to reproduce

No good steps to reproduce. Either use Configuration Inspector to check the type or use #2546212: Entity view/form mode formatter/widget settings have no translation UI to get a translation UI for entity view displays and verify there that you can't translate the label.

Proposed resolution

Change the type of the setting from string to label, which specifies a translatable string.

Remaining tasks

Review, commit.

User interface changes

None without core patches. When using the core patch mentioned above, the label will now be translatable in the config translation UI.

API changes

None.

Data model changes

Config schema type updated for one field formatter setting.

Issue fork reference_value_pair-3526262

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3526262-update-config-schema changes, plain diff MR !5
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