Commit 2021-05-26 21:50 0970fda6

feat(measure_theory/regular): more material on regular measures (#7680) This PR:

• defines weakly regular measures
• shows that for weakly regular measures any finite measure set can be approximated from inside by closed sets
• shows that for regular measures any finite measure set can be approximated from inside by compact sets
• shows that any finite measure on a metric space is weakly regular
• shows that any locally finite measure on a sigma compact locally compact metric space is regular