John/fix-otlp-response (#969)

https://datadoghq.atlassian.net/browse/SVLS-8003

## Overview
Our extension accepts OTLP protobuf requests, and returns a json
response. This break the OTLP spec - a protobuf request should have a
protobuf response. See
https://opentelemetry.io/docs/specs/otlp/#otlphttp-response.

This PR updates our agent to return a protobuf response.

## Testing 
Added integration test to confirm.

Author: jchrostek-dd

bottlecap/Cargo.lock

@@ -43,6 +43,7 @@ rustls-pki-types = { version = "1.0", default-features = false }
 hyper-rustls = { version = "0.27.7", default-features = false }
 rand = { version = "0.8", default-features = false }
 prost = { version = "0.13", default-features = false }
+tonic-types = { version = "0.12", default-features = false }
 zstd = { version = "0.13.3", default-features = false }
 futures = { version = "0.3.31", default-features = false }
 serde-aux = { version = "4.7", default-features = false }

bottlecap/Cargo.toml

@@ -149,6 +149,7 @@ proc-macro2,https://github.com/dtolnay/proc-macro2,MIT OR Apache-2.0,"David Toln
 proc-macro2-diagnostics,https://github.com/SergioBenitez/proc-macro2-diagnostics,MIT OR Apache-2.0,Sergio Benitez <sb@sergio.bz>
 prost,https://github.com/tokio-rs/prost,Apache-2.0,"Dan Burkert <dan@danburkert.com>, Lucio Franco <luciofranco14@gmail.com>, Casper Meijn <casper@meijn.net>, Tokio Contributors <team@tokio.rs>"
 prost-derive,https://github.com/tokio-rs/prost,Apache-2.0,"Dan Burkert <dan@danburkert.com>, Lucio Franco <luciofranco14@gmail.com>, Casper Meijn <casper@meijn.net>, Tokio Contributors <team@tokio.rs>"
+prost-types,https://github.com/tokio-rs/prost,Apache-2.0,"Dan Burkert <dan@danburkert.com>, Lucio Franco <luciofranco14@gmail.com>, Casper Meijn <casper@meijn.net>, Tokio Contributors <team@tokio.rs>"
 protobuf,https://github.com/stepancheg/rust-protobuf,MIT,Stepan Koltsov <stepan.koltsov@gmail.com>
 protobuf-support,https://github.com/stepancheg/rust-protobuf,MIT,Stepan Koltsov <stepan.koltsov@gmail.com>
 quick-error,http://github.com/tailhook/quick-error,MIT OR Apache-2.0,"Paul Colomiets <paul@colomiets.name>, Colin Kiegel <kiegel@gmx.de>"
@@ -226,6 +227,7 @@ tokio-rustls,https://github.com/rustls/tokio-rustls,MIT OR Apache-2.0,The tokio-
 tokio-stream,https://github.com/tokio-rs/tokio,MIT,Tokio Contributors <team@tokio.rs>
 tokio-util,https://github.com/tokio-rs/tokio,MIT,Tokio Contributors <team@tokio.rs>
 tonic,https://github.com/hyperium/tonic,MIT,Lucio Franco <luciofranco14@gmail.com>
+tonic-types,https://github.com/hyperium/tonic,MIT,"Lucio Franco <luciofranco14@gmail.com>, Rafael Lemos <flemos.rafael.dev@gmail.com>"
 tower,https://github.com/tower-rs/tower,MIT,Tower Maintainers <team@tower-rs.com>
 tower-http,https://github.com/tower-rs/tower-http,MIT,Tower Maintainers <team@tower-rs.com>
 tower-layer,https://github.com/tower-rs/tower,MIT,Tower Maintainers <team@tower-rs.com>