add semi_cvg_measure_bigcap

[IshiguroYoshihiro]

Motivation for this change

This PR adds lemma semi_cvg_measure_bigcap.
As compared to cvg_measure_bigcap, type of T is generalized from measurableType to algebraOfSetsType.

I also changed one of assumtion of cvg_measure_bigcap.
And in both lemma, assumtions are changed from mu (A 0%N) \is a fin_num to mu (A 0%N) < +oo and the index is shift so that it starts from 0.

if one want to use these lemma for a goal of limit which index starts from 1, I reccomend to use cvg_shiftS .

Checklist

• added corresponding entries in CHANGELOG_UNRELEASED.md

• added corresponding documentation in the headers

Reference: How to document

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