Add grpc proxying to enable bring-your-own-proto

[yaron2]

Closes #3231.
Closes #3096.
Closes #3065.

This PR enables users to work with their existing gRPC protos for service invocation, while still utilizing Dapr's service invocation features like mTLS, API auth, telemetry, access lists etc.

Notes for the reviewer

High level changes made in this PR

1. Access lists functionality moved from pkg/configuration to pkg/acl. This is for the better and ACLs now live in a dedicated and reusable package.
2. Adding Stream trace middleware for gRPC under grpc_diagnostics.go to support users with gRPC streams.
3. Added the use of a gRPC transparent handler that listens to requests for services that Dapr doesn't know about (user services). This is done through the user of this package which I've reviewed. Once the review process is done, I'll make another commit to migrate the relevant code to Dapr with appropriate attributions. The reason is to remove the dependency ownership.
4. Marked this feature as experimental, meaning it's opt-in until it graduates to a stable level.
5. Added unit tests

Two phase review

In order to keep the list of files changed small for the actual code change, I'm waiting with adding the e2e tests. Once the initial review is done, the following will be added:

1. E2E test
2. Code for the transparent proxy handler

[daixiang0]

Could you share more about why choose this grpc proxy and what changes have made?

[artursouza]

LGTM. Please, address the comments above.

[codecov]

Codecov Report

Merging #3277 (dca6e41) into master (62ad4a3) will decrease coverage by 0.07%.
The diff coverage is 58.13%.

@@            Coverage Diff             @@
##           master    #3277      +/-   ##
==========================================
- Coverage   59.36%   59.28%   -0.08%     
==========================================
  Files          87       91       +4     
  Lines        7806     7973     +167     
==========================================
+ Hits         4634     4727      +93     
- Misses       2855     2919      +64     
- Partials      317      327      +10     

Impacted Files	Coverage Δ
pkg/actors/actors.go	57.11% <0.00%> (ø)
pkg/config/configuration.go	71.01% <ø> (-2.79%)	⬇️
pkg/grpc/api.go	61.13% <0.00%> (+3.22%)	⬆️
pkg/messaging/direct_messaging.go	25.00% <0.00%> (-1.97%)	⬇️
pkg/runtime/cli.go	4.54% <0.00%> (ø)
pkg/runtime/runtime.go	51.98% <0.00%> (-0.32%)	⬇️
pkg/grpc/server.go	18.80% <8.33%> (-1.20%)	⬇️
pkg/diagnostics/grpc_tracing.go	64.66% <31.57%> (-15.15%)	⬇️
pkg/acl/acl.go	62.24% <62.24%> (ø)
pkg/grpc/grpc.go	48.27% <66.66%> (+0.90%)	⬆️
... and 7 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 62ad4a3...dca6e41. Read the comment docs.

[yaron2]

Could you share more about why choose this grpc proxy and what changes have made?

I chose this library as it's complete functionality wise, very well tested, and has no dependencies other than Go stdlib and grpc libraries.

[yaron2]

LGTM. Please, address the comments above.

Ok, I'll now move into the second phase which is E2E and the porting of the proxy library.

[yaron2]

Proxy porting is done.