Add some basic tests for env interface

[rejuvyesh]

I am not sure about hopper:

MethodError: no method matching initialize_walker!(::Mechanism{Float64, 23, 7, 7, 9}; z=0.25)

because it doesn't take z and rather only takes body_position and body_orientation.

Same happens with walker.

Edit I have also renamed :box to :block and fixed its use everywhere I could find.

[rejuvyesh]

For now, I am disabling tests for hopper, rexhopper and walker and this would be good to merge.

[codecov-commenter]

Codecov Report

Merging #12 (ab86d79) into main (0d54f76) will decrease coverage by 0.14%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #12      +/-   ##
==========================================
- Coverage   92.45%   92.31%   -0.15%     
==========================================
  Files          81       81              
  Lines        4005     3761     -244     
==========================================
- Hits         3703     3472     -231     
+ Misses        302      289      -13     

Impacted Files	Coverage Δ
src/graph/entry.jl	75.00% <0.00%> (-12.50%)	⬇️
src/contacts/utilities.jl	40.00% <0.00%> (-5.46%)	⬇️
src/orientation/quaternion.jl	82.92% <0.00%> (-5.41%)	⬇️
src/orientation/mapping.jl	36.36% <0.00%> (-5.31%)	⬇️
src/joints/rotational/input.jl	42.10% <0.00%> (-1.49%)	⬇️
src/joints/joint.jl	88.88% <0.00%> (-0.51%)	⬇️
src/contacts/impact.jl	86.20% <0.00%> (-0.46%)	⬇️
src/bodies/set.jl	94.54% <0.00%> (-0.37%)	⬇️
src/mechanism/traversal.jl	95.00% <0.00%> (-0.35%)	⬇️
src/mechanism/urdf.jl	91.78% <0.00%> (-0.33%)	⬇️
... and 44 more

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[janbruedigam]

Looks good, I will create an issue for the three remaining tests.