Upgrade unittest target framework to .NET 8.0

Added AVX and AVX2 to MacOS x86_64 builds

Custom Sampling Pipelines

Rebuilt ChatSession class

build(deps): bump xunit from 2.6.2 to 2.6.3

Bumps [xunit](https://github.com/xunit/xunit) from 2.6.2 to 2.6.3.
- [Commits](https://github.com/xunit/xunit/compare/2.6.2...2.6.3)

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  dependency-type: direct:production
  update-type: version-update:semver-patch
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build(deps): bump xunit.runner.visualstudio from 2.5.4 to 2.5.5

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.5.4 to 2.5.5.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](https://github.com/xunit/visualstudio.xunit/compare/2.5.4...2.5.5)

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🔧 Refactor Semantic Kernel chat completion implementation

- Added BaseSamplingPipeline which provides a base impl of `ISamplingPipeline`
 - Added `DefaultSamplingPipeline` which mimics normal llama.cpp sampling

- Added an example usage to one of the tests

- Added a `Sample` method to `LLamaContext` which uses a custom pipeline
 - Modified all executors to use the custom pipeline if it exists

- Saves with serialized ChatHistory of session
- Only allows use of ChatHistory.Message (instead of raw text)
   for easy post-processing with IHistoryTransform implementation
- Provides History Management methods
- Allows user to regenerate last assistant message

- Refactored the chat completion implementation in `LLamaSharpChatCompletion.cs` to use `StatelessExecutor` instead of `InteractiveExecutor`.
- Updated the chat history prompt in `LLamaSharpChatCompletion.cs` to include a conversation between the assistant and the user.
- Modified the `HistoryTransform` class in `HistoryTransform.cs` to append the assistant role to the chat history prompt.
- Updated the constructor of `LLamaSharpChatCompletion` to accept optional parameters for `historyTransform` and `outputTransform`.
- Modified the `GetChatCompletionsAsync` and `GetChatCompletions` methods in `LLamaSharpChatCompletion.cs` to use the new `StatelessExecutor` and `outputTransform`.
- Updated the `ExtensionMethods.cs` file to include the assistant and system roles in the list of anti-prompts.

Update README.md

Update example to the latest version

ci: fix error in auto-release.

Update README.md

feat: allow customized search path for native library loading.

Update README.md

Minor spelling fixes

build(deps): bump xunit.runner.visualstudio from 2.5.3 to 2.5.4

build(deps): bump Spectre.Console from 0.47.0 to 0.48.0

Bumps [Spectre.Console](https://github.com/spectreconsole/spectre.console) from 0.47.0 to 0.48.0.
- [Release notes](https://github.com/spectreconsole/spectre.console/releases)
- [Commits](https://github.com/spectreconsole/spectre.console/compare/0.47.0...0.48.0)

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updated-dependencies:
- dependency-name: Spectre.Console
  dependency-type: direct:production
  update-type: version-update:semver-minor
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Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.5.3 to 2.5.4.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](https://github.com/xunit/visualstudio.xunit/compare/2.5.3...2.5.4)

---
updated-dependencies:
- dependency-name: xunit.runner.visualstudio
  dependency-type: direct:production
  update-type: version-update:semver-patch
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build(deps): bump Microsoft.VisualStudio.Validation from 17.6.11 to 17.8.8

fix: Chinese encoding error with gb2312.