\Drupal\Core\Entity\EntityTypeInterface label methods docblocks should be to return TranslatableMarkup

This is a pretty frequent thing, to return markup. Let's update the docs.

+++ b/core/lib/Drupal/Core/Entity/EntityType.php
@@ -179,7 +179,7 @@ class EntityType extends PluginDefinition implements EntityTypeInterface {
-   * @var string
+   * @var \Drupal\Core\StringTranslation\TranslatableMarkup

I don't think they always return TranslatableMarkup. Sometimes it is a string. So we should type hint both in many of these places.

string|\Drupal\Core\StringTranslation\TranslatableMarkup

+1 for what @heddn said. It needs to be "stringable", but not necessarily a primitive string. Kicking this back for that; also tagging as a novice issue since this issue is about copying-and-pasting a single change to many docblocks.

Also, based on #2990464: Breadcrumb markup should allow some tags such as italics or strong, anything renderable to a string. Which means sometimes render arrays (yikes!) and FormattableMarkup. So, anything castable to a string or renderable. Not sure how we handle these edges cases in a type hint. Or maybe we don't allow for render arrays in the hint so as to more better communicate we'd like to see string|FormattableMarkup... Which BTW, TranslatableMarkup is an implementation of FormattableMarkup, so maybe we want to hint on FormattableMarkup instead?

FormattableMarkup is an instance of MarkupInterface, so we could in theory type hint to that. I have never seen any of those methods return a render array, so I don't think we need to go that far. string|TranslatableMarkupis probably fine, and would be my preference.

From a theoretical perspective, I'd argue that methods should accept interfaces so it should probably be MarkupInterface but string|TranslatableMarkup should be fine.

Okay, then I think we're good to go.

Committed 2728cbe and pushed to 8.7.x. Thanks!