1) Promote the default UUID request_id implementation to
an actual extension that is required in the build and wire
up all documentation.
2) Add a configuration option to the extension that allows trace
reason packing to be disabled (the default continues to be for it
to be enabled to match existing behavior).
3) Update all documentation for the new behavior.
4) Substantial cleanup of these code paths for clarity and robustness.
Fixes https://github.com/envoyproxy/envoy/issues/11532
Signed-off-by: Matt Klein <mklein@lyft.com>
Mirrored from https://github.com/envoyproxy/envoy @ 07c4c17be61c77d87d2c108b0775f2e606a7ae12