Support a not in-place api's for protect/unprtect

[pabuhler]

The protect/unprotect api's can now operate both in-place or not in-place, depending on the requirements of the caller. The length of the out buffer can now be checked to ensure there is sufficient space. This addresses #322 "provide an new version of protect function that does not corrupt memory" and #569 "Please add a "non inplace" protect and unprotect API"

srtp_driver has been updated so all existing test can be run either in-place or not in-place.

• [x] Document new api and error codes
• [x] Update examples to use new api
• [x] Create separate PR's for all clean up / refactoring commits
• [ ] Follow up with test cleanup and reuse of CHECK macros

[pabuhler]

This PR is set to draft state as it is still a work in progress and can potentially be force updated with breaking changes.