[Evol assembly] Enable evolutionary dynamics & community assembly

[dfalster]

Problem statement

We want to enable evolutionary dynamics using the revised plant package, so that we can investigate questions of community assembly and trait evolution. We previously had this capacity, but it requires revision and simplification. The dynamics of community assembly and trait evolution will be handled via the package plant.assembly

Owner: @dfalster

Issues

• New mutant method plant#362
• Recover ability to run assembly with plant.assembly plant#370
• Fitness fixes plant#379
• Various renames - fitness_approximate_points & others #14
• Swap out grail for anther gp #10
• https://github.com/traitecoevo/plant.assembly/pull/368
• [evol assembly] Port equilibrium methods into package from plant #23

Acceptance criteria

Given a trait-based tradeoff, we can

• estimate fitness of a mutant
• run a resident or residents to demographic equilibrium
• create a fitness landscape
• solve for the evolutionary attractor for traits in 1D & nD
• assemble communities under different assumptions of community assembly