Show additional plugin headers values in wp plugin get <plugin> output

[ernilambar]

• Plugin header RequiresPlugins is also displayed if exists.
• Added feature test for plugin get. One scenario for RequiresPlugins and one with basic test in separate file plugin-get.feature

Related: #407

[swissspidy]

Makes we wonder whether we shouldn't add more information from get_plugin_data to this list by default. For example the RequiresWP and RequiresPHP information could be useful (both added in 5.3), or UpdateURI (added in 5.8)

[ernilambar]

@swissspidy We could keep name, title, author, version, description and status as default fields and other as optional AVAILABLE FIELDS. And for available optional fields we could add those new fields, like requires_plugins, requires_php, etc.

[swissspidy]

Now that #417 is merged, merging main into this branch should fix the tests