This PR improves the error messages produced by invalid pattern-match
alternatives and improves parity in error placement between
pattern-matching tactics and elaborators.
Closes#7170
This PR adds additional infrastructure for error message formatting.
Specifically, it adds convenience formatters for hints and notes,
including the ability to attach code actions to hint messages using a
"Try This"-like widget, along with several convenience formatters for
message data.
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Co-authored-by: Joachim Breitner <mail@joachim-breitner.de>