Fix tryalgo imports to avoid one-level-up export

[VecoMr]

Fixes #72

This PR exports all necessary functions in __init__.py, allowing users to import them directly from tryalgo, for example:

from tryalgo import opt_bin_search_tree1

or, as before:

from tryalgo.dyn_prog_tricks import opt_bin_search_tree1

This change is not breaking, previous import paths remain valid.

To avoid name conflicts:

• The function khun_munkres from khun_munkres_v4 is exported as khun_munkres_v4
• The function subset_sum from subsetsum is exported as subset_sum_basic
• The function subset_sum from subsetsum_divide is exported as subset_sum_divide