Golf proofs and fix typos

[pitmonticone]

• [x] Golf proof of periodicpts_is_mem
• [x] Golf proof of periodic_arbitrary_large_time
• [x] Golf proof of inter_subset_empty_of_inter_empty
• [x] Golf proof of separated_balls
• [x] Golf proof of separated_ball_image_ball
• [x] Golf proof of separated_balls_along_non_periodic_orbit
• [x] Golf proof of ball_non_periodic_arbitrary_large_time
• [x] Golf proof of non_periodic_arbitrary_large_time
• [x] Golf proof of arbitrary_large_time
• [x] Golf proof of is_closed
• [x] Golf proof of is_cpt
• [x] Golf proof of omegaLimit_nonempty
• [x] Golf proof of omegaLimit_nonwandering
• [x] Golf proof of nonWandering_nonempty
• [x] Golf proof of recurrentSet_iff_accumulation_point
• [x] Golf proof of periodicpts_mem_recurrentSet
• [x] Golf proof of recurrentSet_nonwandering
• [x] Golf proof of recurrentSet_of_minimal_is_all_space
• [x] Golf proof of minimalSubset_mem_recurrentSet

[mseri]

Thanks for the PR! We looked at it with @oliver-butterley and we think it is time to merge :)

[oliver-butterley]

Thanks @pitmonticone and @LorenzoLuccioli!