P4runtime

Third minor release for P4Runtime v1.

Changelog:
* API
* P4Runtime was assigned TCP port 9559 by IANA.
* Deprecate `watch` field (int32) in favor of `watch_port` (bytes). This allows using the watch port feature with the `p4runtime_translation` feature.
* specification
* Move "Security considerations" section to P4Runtime server discussion.
* Replace master, slave, master arbitration with more inclusive language: primary, backup, and client arbitration
* Clarify that source locations for annotations are optional in the P4Info message.

Second minor release for P4Runtime v1.

Changelog:
* API
* Add new `OPTIONAL` match kind. At the moment, `OPTIONAL` is only supported by the v1model architecture, and not by PSA. It will eventually be included in the core P4 language.
* Add support in P4Info for structured annotations, which are used to annotate objects with key-value lists or expression lists.
* Add a new `metadata` field of type `bytes` to `TableEntry`. This is more flexible than the now deprecated `controller_metadata` field.
* Add the ability to change the ID of table match fields, action parameters, Packet IO metadata fields, and Value Set match fields in P4Info by using the `id` annotation.
* Support using `string` as the controller type in the `p4runtime_translation` annotation. Update syntax when using a fixed-width unsigned bitstring as the controller type.
* Add optional P4 source locations to both structured and unstructured annotations.
* specification
* Clarify the behavior of some corner cases involving action profiles and selectors, including the watch port feature.
* build
* Overhaul of the Bazel build system
* Fix rules: remove dependency on `stackb/rules_proto`, use `bazelbuild/rules_proto` instead,
* Improve documentation.
* Add an example Bazel project depending on the P4Runtime rules.

Second release candidate for P4Runtime v1.2.0. Includes improved Bazel support.

First release candidate for P4Runtime v1.2.0.

First minor release for P4Runtime v1.

Almost identical to the [v1.1.0-rc.1](https://github.com/p4lang/p4runtime/releases/tag/v1.1.0-rc.1) pre-release, so refer to the release notes for that release. The only change is an edit to the specification to fix an inconsistency in the section describing consistency requirements for `Write` RPCs.

First release candidate for the first minor release for P4Runtime v1. Should not break backwards-compatibility at the P4Runtime message level. However, some significant changes were made to master-arbitration which will impact controller-failover for client and server implementations.

Changelog (copied from the Revision History Appendix):
* API
* Major overhaul of master-arbitration: while the Protobuf messages did not change, the state machine that the server needs to implement is significantly different. Upon the master disconnection, the server no longer chooses the controller with the second highest election id as the new master. Instead, there will not be a new master until one of the controllers advertises an election id higher than any election id seen previously.
* Add `error` field to stream messages sent by the server.
* Add `Capabilities` RPC to query the P4Runtime API version implemented by the server.
* Support wildcard reads for multicast groups and clone sessions.
* Support for modifying direct resources of const tables.
* Support P4 user-defined types for Packet IO metadata fields.
* specification
* Clarify consistency requirements for `Write` and `Read` RPCs.
* Add Appendix providing implementation advice for avoiding common pitfalls:
* advice on setting gRPC Metadata Maximum Size
* advice on setting gRPC Server Maximum Receive Message Size
* Clarify limitations on supported types for `FieldMatch`, action `Param`, and Packet IO metadata fields.
* Clarify that reading entire forwarding state with empty `entity` is not supported.
* Document that `p4runtime_translation` need only be supported when applied to type declarations in P4.