Make singleton element of LanguageServerDefinition configurable

[ghentschke]

It should be possible to set the singleton attribute of the LanguageServerDefinition via an interface. This allows the definition of multiple LS per workspace or not depending on preferences.

User story: As a vendor supplier I want to use different language server in one workspace. The servers are toolchain specific.

WDYT?

[mickaelistria]

Preferences usually reprensent items that are to be configured by users. Can you please clarify about your use-case where you'd like to dynamically flip the singleton behavior on/off ? Wouldn't it be possible for you to programatically define the LanguageServerDefinition and add it to the registry?

[ghentschke]

Wouldn't it be possible for you to programatically define the LanguageServerDefinition and add it to the registry?

Wouldn't that imply another LSP4E extension point which has an element which contains a class which has to extend LanguageServerDefinition ?