Estimators should have containing node

Estimators tags should be enclosed in containing node

```xml

10 10 10



0.0 0.0 0.0


3.37316115 3.37316115 0.00000000
0.00000000 3.37316115 3.37316115
3.37316115 0.00000000 3.37316115

...

```
This would allow EstimatorManagerInput to be responsible for the parsing of everything within that node and allow it to raise error if it can't parse child nodes or dispatch them to specific estimator input classes.

Currently the EstimatorManagerNew gets the driver node and scans through the child nodes reading the estimator nodes as the legacy estimator manager did.

**Describe the solution you'd like**
As above

**Describe alternatives you've considered**
Pass collection of child nodes from the driver.
Driver somehow keeps track that those nodes were delegated.

**Additional context**
This is more consistent with the way Hamiltonians and WaveFunctions are defined.
Estimator Sets could be named defined at "global" scope, and used by name in qmc sections i.e.

```xml

...

...

or

best_estimator_set
...

```
Whether this is a good idea is debatable.