Adds Complex#deconstruct as an alias for Complex#rect.

Reasoning and usefulness

• I am not aware of complex literals with real parts, mandating the use of the pin operator in patterns (and only for exact comparisons).
• The Syntax of complex array patterns is identical to Kernel#Complex.
• It allows constraints on the real and imaginary parts of the number.
• Complex already implements the functionality as rect, this just makes it available to patterns.

Usage

Complex(1, 2) in Complex(1, 2)  # => true (false in Ruby < 4)

# Assert that a Complex is, in fact, a real number and extract the real part.
num = Complex(42, 0)            # => (42+0i)
num => Complex(real, 0)         # => nil
real                            # => 42

Issues

• Is the test sufficient and in the right place?