docs/ste-expected-checksums trusted vs integrity verification

### Affected version

HEAD

### Bug description

There are internal contradictions in this document about the purposes of checksums. Trusted checksums are not just about integrity verification. And this extends to some other docs too.

This needs to be straightened out

Start by reading the docs/ste-expected-checksums document and identify the statements that distinguish trusted checksums from integrity verification. Search the related documentation mentioned in the issue for the same contradiction; done means the explanations consistently describe the purposes of both checksum uses.

Written by the indexing model from the issue text.