[PINS] update sonic-p4rt docker to bullseye (#10182)

#### Why I did it
SONiC is migrating to bullseye. This will update the sonic-pins container to bullseye.

#### How I did it
The [sonic-pins code](https://github.com/Azure/sonic-buildimage/blob/master/rules/p4rt.mk) isn't dependent on any architecture so it will already build successfully for bullseye. This PR updates the docker to use bullseye.

#### How to verify it
Today we cannot build the docker-sonic-p4rt.gz target (e.g. Issue #9885). With this change the docker will build successfully. The P4RT executable will not run, because of a missing runtime library, libgmpxx, which I'll address in a followup PR.

#### Description for the changelog
Update docker-sonic-p4rt.gz target to build with Bullseye instead of Buster.

dockers/docker-sonic-p4rt/Dockerfile.j2

@@ -1,5 +1,5 @@
 {% from "dockers/dockerfile-macros.j2" import install_debian_packages, install_python_wheels, copy_files %}
-FROM docker-config-engine-buster
+FROM docker-config-engine-bullseye
 
 ARG docker_container_name
 ARG git_commit

rules/docker-p4rt.mk

@@ -7,12 +7,12 @@ DOCKER_P4RT_DBG = $(DOCKER_P4RT_STEM)-$(DBG_IMAGE_MARK).gz
 $(DOCKER_P4RT)_PATH = $(DOCKERS_PATH)/$(DOCKER_P4RT_STEM)
 
 $(DOCKER_P4RT)_DEPENDS += $(SONIC_P4RT)
-$(DOCKER_P4RT)_DBG_DEPENDS = $($(DOCKER_CONFIG_ENGINE_BUSTER)_DBG_DEPENDS)
+$(DOCKER_P4RT)_DBG_DEPENDS = $($(DOCKER_CONFIG_ENGINE_BULLSEYE)_DBG_DEPENDS)
 $(DOCKER_P4RT)_DBG_DEPENDS += $(SONIC_P4RT_DBG) $(LIBSWSSCOMMON_DBG)
 $(DOCKER_P4RT)_DBG_DEPENDS += $(LIBSAIREDIS_DBG)
-$(DOCKER_P4RT)_DBG_IMAGE_PACKAGES = $($(DOCKER_CONFIG_ENGINE_BUSTER)_DBG_IMAGE_PACKAGES)
+$(DOCKER_P4RT)_DBG_IMAGE_PACKAGES = $($(DOCKER_CONFIG_ENGINE_BULLSEYE)_DBG_IMAGE_PACKAGES)
 
-$(DOCKER_P4RT)_LOAD_DOCKERS += $(DOCKER_CONFIG_ENGINE_BUSTER)
+$(DOCKER_P4RT)_LOAD_DOCKERS += $(DOCKER_CONFIG_ENGINE_BULLSEYE)
 
 $(DOCKER_P4RT)_VERSION = 1.0.0
 $(DOCKER_P4RT)_PACKAGE_NAME = p4rt