Deprecate unbound method usage

Convert public arrow function class fields back to regular prototype
methods and wrap them with `deprecatedBoundMethods` in the constructor
for backwards compatibility.

When a method is called with a lost `this` (e.g. via destructuring),
a per-method deprecation warning is emitted once. In the next major
the wrappers will be removed and unbound calls will fail.

Closes #300

Signed-off-by: Jon Koops <jonkoops@gmail.com>

Set version to 26.2.4

Set version to 26.2.3

Set version to 26.2.2

Set version to 26.2.1

Set version to 26.2.0