Bugs/fix 2487 allow contains whitespaces

[JKamsker]

Fixes #2487 and contains a minor perf improvement

[pictos]

@JKamsker we do have a failing build, can you verify the reason?

[JKamsker]

@JKamsker we do have a failing build, can you verify the reason?

Debug builds just fine, release doesnt.
Because: https://github.com/mbdavid/LiteDB/blob/610e530bb2d70be9718777dff0ebaba66a3d9cdd/LiteDB/Utils/Constants.cs#L7-L10
And CreateEngine in https://github.com/mbdavid/LiteDB/blob/fad6af353d86514faa90e46e3db1efb73369331e/LiteDB.Tests/Issues/Issue2487_Tests.cs#L22

Which is internal
https://github.com/mbdavid/LiteDB/blob/610e530bb2d70be9718777dff0ebaba66a3d9cdd/LiteDB/Client/Structures/ConnectionString.cs#L110

@pictos Do you think its safe to remove the #if DEBUG in Constants ? Otherwise we cant test release builds. I Have no idea whats the benefit of InternalsVisibleTo when you cant use it half of the time.