Initial fluentd support (#205)

* fix(hack): use sudo -E when running Rust binaries

This makes it possible to pass envvars to the Krata runtime

* feat(o11y): add fluent sink to logs

This change adds fluent logging as an opt-in feature. Setting
`KRATA_LOG_FLUENT` with an address:port will start a TCP connection,
sending logs.

A later changes will respect a URI scheme and use structured logging.

hack/debug/common.sh

@@ -28,5 +28,5 @@ build_and_run() {
   fi
   RUST_TARGET="$(./hack/build/target.sh)"
   ./hack/build/cargo.sh build ${CARGO_BUILD_FLAGS} --bin "${EXE_TARGET}"
-  exec sudo sh -c "RUST_LOG='${RUST_LOG}' 'target/${RUST_TARGET}/debug/${EXE_TARGET}' $*"
+  exec sudo -E sh -c "RUST_LOG='${RUST_LOG}' 'target/${RUST_TARGET}/debug/${EXE_TARGET}' $*"
 }