Restore search engine and supporting components and add support for configurable debug logging - #13

Converting null literal or possible null value to non-nullable type.

Converting null literal or possible null value to non-nullable type.

Possible null reference argument for parameter 'key' in 'bool Dictionary<string, CompiledFilterOp>.TryGetValue(string key, out CompiledFilterOp value)'.

Converting null literal or possible null value to non-nullable type.

Dereference of a possibly null reference.

The variable 'count' is assigned but its value is never used

Possible null reference argument for parameter 'term' in 'void FstBuilder.AddForwardOnly(string term, int output)'.

Dereference of a possibly null reference.

Obsolete member 'Span2D<T>.GetHashCode()' overrides non-obsolete member 'object.GetHashCode()'