Fix import context with style (drawing layer)

[pelord]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines:https://github.com/infra-geo-ouverte/igo2/blob/master/.github/CONTRIBUTING.md#git-commit-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What is the current behavior? (You can also link to an open issue here)
this behavior related to #1337

What is the new behavior?
1- Store the feature style as an igoStyleObject within _style property.
2- Store the label inside the _mapTitle property.

Overall, this PR propose to use existing mecanism to handle styles during import (context or data). This is a "temporary" fix. I think we need to create a new layer type or extend the vector type, to handle internal layer types (draw, directions, measures) to be handled easily, on export/import.

Furthermore, the style handling will be changed shortly by using the geostyler library.

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

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

Other information:

[aziz-access]

For style exporting is done with draw layers. but with importing we have issue with circles and points radius.
the radius changes with zoom level.
I think this related to projection 'EPSG:4326'.
Example: Circles 100km - zoom: 6.

Example: Circle 100km - zoom: 5.

[pelord]

Does your PR (#1359) fix this issue?

[aziz-access]

yes, we need your confirmation