LLamaToken Struct

- made `llama_backend_init` private. This is automatically called, there is no way it can correctly be used externally.
 - made `llama_token_to_piece` safe (Span instead of pointer)

- Wrapped some native functions which take (pointer, length) in function which take a `span` instead.

- Made `NativeApi` into a `static class` (it's not intended to be instantiated)
 - Moved `LLamaTokenType` enum out into a separate file
 - Made `LLamaSeqId` and `LLamaPos` into `record struct`, convenient to have equality etc

- Enabled more features in build process (VBMI and VNNI)
 - Added runtime checking for this features
 - Improved runtime checking to no longer require dotnet8.0

Context Set Seed

Renamed `llama_sample_temperature` to `llama_sample_temp`

- Renamed `LLamaModelKvOverride` to `LLamaModelMetadataOverride`

- build run: https://github.com/SciSharp/LLamaSharp/actions/runs/7196891440
 - commit: 9fb13f9584

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

feat: allow customized search path for native library loading.

- Built by this run: https://github.com/SciSharp/LLamaSharp/actions/runs/6921572568
 - commit: `e937066420b79a757bf80e9836eb12b88420a218`
 - Rearranged paths

FixedSizeQueue:
 - Enqueue would always stop one short of filling the capacity
 - Fill would only _replace_ existing items. It was only used in a place where there were not existing items! Removed the method entirely.

LLamaGrammarElement:
 - Converted into a `record` struct, removed all of the (now unnecessary) equality stuff.

Added Obsolete markings to all `Eval` overloads

dotnet8.0

Originally from these PRs:
 - https://github.com/SciSharp/LLamaSharp/pull/263
 - https://github.com/SciSharp/LLamaSharp/pull/259

CPU Feature Detection 2

MinP Sampler