fix: change default collation allowance

[Climax777]

Make provision for C_COLLATION_OID and POSIX_COLLATION_OID, which are also built-in types.

I'm not 100% sure what the impact will be, but everywhere specifically DEFAULT_COLLATION_OID was used, the other two are allowed now as well.

This fixes #169 and pushes down ObjectID queries for all columns.

[vaibhavdalvi93]

@Climax777 , Thanks for the patches. At a glance, changes looks good to me. However, I will have a deeper look into it.

[Climax777]

I found out that $in and $expr cannot make use of indexes. Only equality tests.

I will work in a bigger patch for normal top level $match requests to be flattened and just use normal query style formatting.

Should I rather make a new pull request to keep things simple and clear?