The authoritative source of which built structures currently exist.

The two type parameters, b and a, correspond to Cell and Entity, respectively.

Bulk insertion of structures statically placed in the scenario definition.

See the docs for initializeRecognition for more context.

Note that if any of these pre-placed structures overlap, we can't be sure of the author's intent as to which member of the overlap should take precedence, so perhaps it would be ideal to throw an error at scenario parse time.

However, determining whether a structure is all three of: 1. placed 2. still recognizable 3. overlapping with another recognized structure occurs at a later phase than scenario parse; it requires access to the GameState.

So we just use the same sorting criteria as the one used to resolve recognition conflicts at entity placement time (see [STRUCTURE RECOGNIZER CONFLICT RESOLUTION]).

We use a NEMap here so that we can use the safe-indexing function indexWrapNonEmpty in the implementation of the structure command.

This is a worldwide "mask" that prevents members of placed structures from participating in new structures and facilitates deletion of structures when their elements are removed from the world.

Each recognized structure instance will have MxN entries in this map.