Backport fixes from 1.8.7+dfsg1-5 to fix build failure

Build was failing with,

Generating proto/pbconnect/connect.proto into proto/pbconnect/connect.pb.go and proto/pbconnect/connect.pb.binary.go
protobuf: warning: directory does not exist.
--proto_path passed empty directory name.  (Use "." for current directory.)
Failed to generate outputs from proto/pbconnect/connect.proto

Backport the below commits to fix the build error,

https://salsa.debian.org/go-team/packages/consul/-/commit/6c2911d96a7d15b8ac9d46292ed1bba1af6a1692
https://salsa.debian.org/go-team/packages/consul/-/commit/94e1a2ee48397d86b33be9d8010979673f2e24df
https://salsa.debian.org/go-team/packages/consul/-/commit/0ff5f561e8e4522154ba693fbf98bb4b5c4874a5
https://salsa.debian.org/go-team/packages/consul/-/commit/0cedb673ede028e2e57ad18dfd99f8fd8b2d1956

Closes: #982931

Fixes: https://phabricator.apertis.org/T8781