Display version of custom plugins

[FNI18300]

Description

The PR corresponds to #11256

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:

Issue

What is the current behavior?
The aim of this proposal is to display the version of custom plugins into MapStore2.
It seems that the best place to display this information is the step 3 when we create MapStore Context, when we display 2 lists (one with available plugins, one with activated plugins).
see #11256

What is the new behavior?
If the index.json file provided with the plugin zip contains the property "version" with a defined value, this information is displayed in the context creator module

Breaking change

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

• Yes, and I documented them in migration notes
• No

[FNI18300]

This proposal is linked to geosolutions-it/MapStoreExtension#67 which add a simple way to enhanced the index.json with the version presents in version.txt file.