Algorithm Suites doc security consideration section

Expand on the security consideration section to add the following:

- answer common question "why is no salt used for HKDF?"
- List security properties of the algorithm suites.

Locate the Algorithm Suites security consideration section in the specification and review its surrounding terminology before drafting the two requested additions. Done means the section explains why HKDF uses no salt and lists the algorithm suites' security properties, with the documentation rendering cleanly.

Written by the indexing model from the issue text.