[main] Update envoy to v1.21.0 (#2330)

* upgrade envoy and remove boringssl

* update changelog

* update envoy

Co-authored-by: Henry Li <[email protected]>

Author: henryli001

SPECS/LICENSES-AND-NOTICES/LICENSES-MAP.md

@@ -2497,7 +2497,6 @@
                 "bea-stax",
                 "beust-jcommander",
                 "bnd-maven-plugin",
-                "boringssl",
                 "bouncycastle",
                 "bsf",
                 "bsh2",