DocumentSelection#markers collection should be updated only for observed markers groups

[niegowski]

Suggested merge commit message (convention)

Other (engine): The DocumentSelection#markers collection is updated only for observed markers groups.

BREAKING CHANGE (engine): The DocumentSelection#markers collection is no longer enabled by default. DocumentSelection#observeMarkersGroup() must be used to register markers group to be observed.

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Additional information

This is performance optimization.

[scofalik]

I left some review comments, minor stuff.

I have one doubt, though. This is connected with the fact that we never forced any structure for markers and something like "marker group" was not really specified (outside of API docs). It just appeared that in 99% of cases there are multiple markers of the same type and it makes sense to handle all of them in the same way. Hence, we have comment: and suggestion: and "marker groups" were born and we try to describe what's "marker group" where possible. I am not sure if this is clear to our users.

The problem is that it is still possible to create a marker with a name that does not have :. We should handle them as well. For example, someone could implement find and replace and use marker named searchResult to highlight the current result. So, in places where we check whether we should observe given marker, we should probably check whether prefix matches and if not, whether full name matches. And include this case in API docs for observeMarkersGroup. Maybe we should also rename that method to observeMarkers or observeMarkersNames or something?