1) Some intro text felt out of date as well as minor changes to
the overall flow.
2) Small fix to extauth docs from recent issue.
3) Remove ambassador/gloo docs. Almost definitely out of date and
don't belong anymore given how many things consume Envoy.
4) Remove TapDS. It was never implemented and would never be
implemented given ECDS.
5) Fix release notes from stable releases.
Signed-off-by: Matt Klein <mklein@lyft.com>
Mirrored from https://github.com/envoyproxy/envoy @ 50e722cbb0486268c128b0f1d0ef76217387799f