### Motivation and Context

This PR adds a few building blocks for gRPC skills support. The rest of
the functionality - gRPC skills import, support for complex data
contract, retries, etc. will/might be added later.

### Description
This PR add the following classes/components:
- Skills.Grpc - project/package added to keep gRPC related
functionality.
- ProtoDocumentParser - class responsible for parsing .ptoto files and
extract them into a list of operations represented by GrpcOperation
class.
- GrpcOperation - model class that describes a gRPC operation.
- GrpcOperationRunner - class responsible for running a gRPC operation.

### Contribution Checklist
<!-- Before submitting this PR, please make sure: -->
- [x] The code builds clean without any errors or warnings
- [x] The PR follows SK Contribution Guidelines
(https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
- [x] The code follows the .NET coding conventions
(https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions)
verified with `dotnet format`
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

---------

Co-authored-by: Shawn Callegari <36091529+shawncal@users.noreply.github.com>

### Motivation and Context

This change adds functionality required for gRPC skills import to Kernel
allowing SK SDK client code to register and use gRPC skills in SK SDK.

### Description
This change adds a few ImportGrpc* Kernel extension methods that can
import gRPC skills from a folder or a file. Additionality,
GrpcOperationRunner is changed to accept gRPC request message as JSON
and return the gRPC method result as JSON as well.

### Contribution Checklist
<!-- Before submitting this PR, please make sure: -->
- [x] The code builds clean without any errors or warnings
- [x] The PR follows SK Contribution Guidelines
(https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
- [x] The code follows the .NET coding conventions
(https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions)
verified with `dotnet format`
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

…) with a sample proto file (#768)

### Motivation and Context
This is related to #451,
craigomatic#13, and
craigomatic#16, where we want to
demonstrate how Native skills can be invoked via gRPC and implemented
across various languages. In this case, we are specifically implementing
this polyglot Native skill in Java due to customer inquiries.


### Description
This change introduces a sample Java application that functions as a
gRPC server. The `GrpcOperationRunner` can invoke Java code using the
[activity.proto file in this
PR](https://github.com/thegovind/semantic-kernel/blob/feature-grpc/samples/java/JavaReferenceSkill/src/main/proto/activity.proto)
and its operation `GetRandomActivity`, as shown in
[`Example27_GrpcSkills` in
`kernel-syntax-examples`](https://github.com/microsoft/semantic-kernel/pull/730/files#diff-29f0ad84e48c3fe28f2ad26603940927306a57aaf76f6c01fc19e7ac82e33da0).

…h with the main one. (#816)

### Motivation and Context

Fix for the latest, partially successful, merge of gRPC feature branch
with the main one.

### Description

This PR addresses comments made in another PR to merge feature-grpc
branch to the main one. It also contains a small improvement that
prevents creation of HttpClient per each gRPC operation run and use only
one HttpClient instance per set of skills imported together. Later, in
scope of a different task, another improvement will be done to allow
hosting apps to provide their instances of HttpClient, if needed.