Collection operations like `removeAll` should not invalidate references

* [x] I've read, understood, and done my best to follow the [*CONTRIBUTING guidelines](https://github.com/jjatie/Charts/blob/master/CONTRIBUTING.md).

## What did you do?

Call `removeAll` on a DataSet (specifically `LineChartDataSet`, although this applies to many subclasses):

var newSeries = oldSeries
newSeries.removeAll()
assert(newSeries == oldSeries)

## What did you expect to happen?

`removeAll` should remove entries in the data set, while keeping the instance the same.
The assertion should not fail.
In other words, it should not invalidate other references to the data set.

The Charts library has chosen to define data sets as classes (reference types). However,
the inherited methods from the collection protocols are not consistent with reference type semantics.

## What happened instead?

Calling `removeAll` creates a new data set (unless `keepingCapacity: true`). This makes sense for a value type, but it is quite confusing for a reference type.

This can be solved by overriding the default `removeAll` implementation
and doing it properly. For example, the internal `entries` array can be thrown away and recreated, without invalidating the entire ChartDataSet object.

## Charts Environment

**Charts version/Branch/Commit Number:** 4.1.0
**Xcode version:** 14.0.1
**Swift version:**
**Platform(s) running Charts:** iOS