Use SearchValues<string> in TextLiteral with net9.0

[sebastienros]

Also change the parser to accept a list of strings (as ORs).
SearchValues<string> supports case sensitive searches. c.f. https://medium.com/codenx/searchvalues-in-net-8-and-net-9-42b88444eefa

[sebastienros]

TextLiteral is not better when using a single string in SearchValues<string> as the current implementation uses a direct ROS comparison the buffer (though maybe vectorization still makes it better?). However it might be useful for multiple strings, like OneOf(Text("hello"), Text("world")) though again a lookup table might already be best thing.