Dynamic system instructions

[nsarrazin]

This PR takes over from #942 as it's more versatile and can be expanded with more features in the future.

The links are parsed as plain text directly. You can click on them directly to follow them.

The prompt in the example would give something like this

"<s> [INST]Your goal is to make the user guess a country. \r\n\r\nThe country of the day is: **American Samoa**\r\n\r\nAlso today is 3/21/2024 but you can also add spaces 3/21/2024\r\n\r\nAnd this is not a {{ valid tag }} so it doesn't get highlighted\r\n\r\n{{ really {{ really ?? }} }} [/INST]"