Add an Example and modifications to the interactive executor to enable Llava Models.

Just a preview / demo

Conversations can be "forked", to create a copy of a conversation at a given point. This allows e.g. prompting a conversation with a system prefix just once and then forking it again and again for each individual conversation. Conversations can also be "rewound" to an earlier state.

Added two new examples, demonstrating forking and rewinding.

- Added `logits_i` argument to `Context.ApplyPenalty`
 - Added a new exception type for `llama_decode` return code

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

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.

- Cleaned up comments in implementations of `IInferenceParams`
 - Removed default values for all parameters in `LLamaContext.Sample` - they're never used and probably _shouldn't_ ever be used

had to update binary to `b1426`

- Passing `ILogger` into executors

Changed `OpenOrCreate` to `Create`

- Just convert it to a `string`, nice and simple
 - Write the bytes to a `Span<byte>` no allocations
 - Write the chars to a `StringBuilder` potentially no allocations

- Minor changes to cleanup some of the compiler warnings

- Deleted `NativeInfo` (internal class, not used anywhere)

- Removed some unnecessary `ToArray` calls
 - Initial pass on LLamaStatelessExecutor, the context overflow management is broken but I think I found where it's ported from

- Integrated grammar into sampling
 - Added a test for the grammar sampling

The biggest single change is renaming `LLamaModel` to `LLamaContext`

Fix serialization error due to NaN

- Also refactored it to return an `int[]` instead of an `IEnumerable<int>`, solving the "multiple enumeration" problems at the source!