Tink version 1.6.1

Version bump to 1.6.1.

PiperOrigin-RevId: 384286927
(cherry picked from commit 99d3796)

Tink version 1.6.0

Resuming 1.6.0 release.

PiperOrigin-RevId: 374257581

Tink version 1.5.0

Enable GitHub CodeQL scanning.

PiperOrigin-RevId: 337409066

Tink version 1.4.0

Merge branch '1.4' of github.com:google/tink into 1.4

Merge branch '1.4' of github.com:google/tink into 1.4

Tink version 1.4.0-rc2