[custom] Remove empty destructors and constructors

This issue is to split PR #4249 into smaller pieces.

Per @SergioRAgostinho

With destructors I use the following policy:

if your class defines virtual methods which it defines (literally defining, not overriding), I explicitly default it. The compiler throws warnings telling if of your class has virtual methods but the destructor is not virtual.

If a class has empty / default destructors I just remove those lines of code. If the destructor is not implicitly generated you'll get a compiler error, so there's no chance you'll mess up.

For constructors: remove all default constructors unless there's a user defined (non-default) constructor.

From @kunaltyagi: https://godbolt.org/z/8f99dG