Get rid of stale branches `match-matcher` and `linalg-semantics`

[lephe]

These two branches are probably irrelevant now:

• The changes on match-matcher should already be in rewriter which is planned for merging in the future.
• The changes on linalg-semantics should already be in linalg-theorems which is the next big branch to merge.

@bollu @math-fehr could you check these and delete them if they're indeed irrelevant?

[math-fehr]

Done for match-matcher