Modify Contextual MAB param

[maypink]

Add possibility to specify context agent as Callable function (if its a custom function) and as ContextAgentTypeEnum

[codecov-commenter]

Codecov Report

Merging #167 (29640f5) into main (8aaf543) will increase coverage by 0.00%.
Report is 1 commits behind head on main.
The diff coverage is 62.50%.

@@           Coverage Diff           @@
##             main     #167   +/-   ##
=======================================
  Coverage   74.13%   74.13%           
=======================================
  Files         129      129           
  Lines        7673     7678    +5     
=======================================
+ Hits         5688     5692    +4     
- Misses       1985     1986    +1     

Files Changed	Coverage Δ
...olem/core/optimisers/genetic/operators/mutation.py	91.00% <ø> (ø)
...misers/adaptive/mab_agents/contextual_mab_agent.py	32.20% <50.00%> (ø)
golem/core/optimisers/opt_node_factory.py	83.87% <66.66%> (-4.60%)	⬇️

... and 3 files with indirect coverage changes