Rule S4790: its content should be replaced by S2070

For hashing algorithms, several rules exist, in particular these two:

• A security-hotspot: https://jira.sonarsource.com/browse/RSPEC-4790
• That supersedes this vulnerability: https://jira.sonarsource.com/browse/RSPEC-2070

It's not possible to maintain two rules on exactly the same subject, for us and the end users, so:

• S2070 will be deprecated
• the content/implementation of S2070 is more relevant than S4790 because S4790 raises everywhere a hash function is used (even when secure hash function, like SHA-256 is used) and S2070 raises only when a weak hash function is used (like MD5)
• so the content/implementation of S2070 should "be moved" to S4790 (the key of the rule should be updated in SonarJava), because the type of issue (hotspot) is more relevant