Merge branch 'robbert/twp_vals_compare_safe' into 'master'

Also use `solve_vals_compare_safe` in TWP case of `wp_pure`.

See merge request !444
2 jobs for master in 21 minutes and 52 seconds (queued for 2 seconds)
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  Build
passed build-stdpp.dev-coq.8.11.1 #70698
fp

00:11:19

passed build-stdpp.dev-coq.dev #70699
fp

00:21:51