ConstantScoreQuery looses explain details of wrapped query [LUCENE-8606]

Right now the ConstantScoreWeigth used by the ConstantScoreQuery is not adding the details of the wrapped query to the explanation.

```Java
if (exists) {
return Explanation.match(score, getQuery().toString() + (score == 1f ? "" : "^" + score));
} else {
return Explanation.noMatch(getQuery().toString() + " doesn't match id " + doc);
}
```

This is kind of inconvenient as it makes it kind of hard to figure out which term finally really matched when one e.g. puts a BooleanQuery into the FILTER clause of another BooleanQuery.

---
Migrated from [LUCENE-8606](https://issues.apache.org/jira/browse/LUCENE-8606) by Christian Ziech
Attachments: [0001-LUCENE-8606-adding-a-constructor-for-the-ConstantSco.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-8606/0001-LUCENE-8606-adding-a-constructor-for-the-ConstantSco.patch), [0001-LUCENE-8606-overwriting-the-explain-method-for-Cachi.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-8606/0001-LUCENE-8606-overwriting-the-explain-method-for-Cachi.patch)