[REFACTOR] global variables

Some global vars in package model should be encapsulated in a root object

```go
var maskContextFactories []MaskContextFactory
var maskFactories []MaskFactory
```

Start by locating the package model and every use of maskContextFactories and maskFactories. Read how these globals are initialized and accessed, then determine the root object boundary that should own them. The refactor is done when the factories are encapsulated there and the existing behavior remains covered by the project's tests.

Written by the indexing model from the issue text.