DX for translatable entities: Exception when omitting the "data_table" for entity types

Problem/Motivation

When writing contrib modules with custom entities, hard-to-interpret SQL exceptions can hit developers.

This issue provides a patch with an alternative approach to Omitting the "base_table" or "data_table" for entity types is broken.

While there is movement in Deprecate table names from entity definitions to remove

Proposed resolution

• Add more explicit exception texts to speed up development. In particular, it helps with "broken"ContentEntityType annotations.
• Add a test for these exceptions.

Remaining tasks

Review and commit.

User interface changes

None.

API changes

None.