Description

This pr fixes some issues on the toc: on related to the way new groups are added and one on the delete of the layers and all the group hiearchy that has no layers in the sub-tree

• By doing that it also accomplish the group deletion if all layers of that group are selected and you hit delete all the levels trash button (maybe we can change the name with "Delete all the layers and groups"
• Maybe we can make the regex used to filter which groups name can be created configurable.
  @tdipisa opinions?

Issues

• Fix Bug in Creating and Managing Layer Groups  #3051

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/geosolutions-it/MapStore2/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x", remove the others)

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior? (You can also link to an open issue here)

What is the new behavior?
It is not possible to create group with empty name.
if you delete a layer in a subgroup and no layers are left then all the group hierarchy is deleted along with the layer

Does this PR introduce a breaking change? (check one with "x", remove the other)

• Yes
• No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:
I've added a TocUtils for all the stuff that is toc related