revamp playing and replaying

[Sid-Bhatia-0]

1. Remove Play module and move all its contents into the GridWorlds module.
2. Remove hardcoded delimiters and simplify the format of the recording file.
3. Don't forward get_action_names for RLBaseEnv type. Only forward show and play! for now.

[codecov-commenter]

Codecov Report

Merging #175 (66d5f7a) into master (f7b8632) will decrease coverage by 0.22%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #175      +/-   ##
==========================================
- Coverage   62.92%   62.70%   -0.23%     
==========================================
  Files          27       27              
  Lines        2654     2665      +11     
==========================================
+ Hits         1670     1671       +1     
- Misses        984      994      +10     

Impacted Files	Coverage Δ
src/play.jl	0.00% <0.00%> (ø)
src/rlbase.jl	25.00% <0.00%> (+5.00%)	⬆️
src/abstract_grid_world.jl	11.00% <0.00%> (-0.92%)	⬇️
src/envs/dynamic_obstacles_directed.jl	57.95% <0.00%> (+2.27%)	⬆️

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