Currently ExpressionContext has multiple constructors that has multiple default values in their arguments.

Multiple commands like find and distinct create the ExpressionContext from the existing constructors and pass multiple attributes that should have been default values

Proposal is to use designated initilizer when constructing ExpressionContext and if constructors are necessary, then we could create a aggregate config struct and use it as the constructor parameter.

The example usage would be like this:

auto pool = ThreadPool({.min_threads = 1, .max_threads=10, .idle_time = Seconds(10)})