DHS code improvements

[shoubhikraj]

• Changes trust radius for optimiser to 0.1 Angstrom (since default step size for DHS is also 0.1 angstrom, anything larger does not make sense)
• Replaces left_coord and right_coord properties of the image pair object with left_coords and right_coords to match with other parts of autodE.

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Checklist

• [x] The changes include an associated explanation of how/why
• [x] Test pass
• [x] Documentation has been updated
• [x] Changelog has been updated

[codecov[bot]]

Codecov Report

Merging #280 (3e50e73) into v1.4.0 (e05752d) will increase coverage by 0.00%. The diff coverage is 97.96%.

@@           Coverage Diff            @@
##           v1.4.0     #280    +/-   ##
========================================
  Coverage   97.32%   97.33%            
========================================
  Files         203      203            
  Lines       22055    22440   +385     
========================================
+ Hits        21466    21841   +375     
- Misses        589      599    +10     

Flag	Coverage Δ
unittests	97.33% <97.96%> (+<0.01%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
autode/transition_states/templates.py	93.85% <ø> (ø)
autode/wrappers/keywords/basis_sets.py	100.00% <ø> (ø)
tests/benchmark.py	0.00% <ø> (ø)
tests/test_opt/setup.py	0.00% <0.00%> (ø)
tests/test_pes/test_rs.py	97.19% <ø> (ø)
autode/transition_states/base.py	73.07% <76.92%> (+1.07%)	:arrow_up:
autode/path/adaptive.py	91.48% <77.77%> (-1.11%)	:arrow_down:
autode/opt/coordinates/internals.py	97.22% <83.33%> (-0.88%)	:arrow_down:
autode/transition_states/transition_state.py	75.00% <86.95%> (+0.32%)	:arrow_up:
autode/opt/optimisers/trust_region.py	94.28% <87.50%> (-0.78%)	:arrow_down:
... and 98 more

[shoubhikraj]

@t-young31 Feel free to merge the PR