loader: unify the loader to only use enabled_dict_names slice for loading both sys and user dict

[kanru]

[codecov[bot]]

Codecov Report

:x: Patch coverage is 68.42105% with 6 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 92.01%. Comparing base (51fb091) to head (3e99d58).

Files with missing lines	Patch %	Lines
src/dictionary/sqlite.rs	0.00%	3 Missing :warning:
src/dictionary/trie.rs	0.00%	3 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #787      +/-   ##
==========================================
- Coverage   92.06%   92.01%   -0.05%     
==========================================
  Files          37       37              
  Lines        9252     9271      +19     
==========================================
+ Hits         8518     8531      +13     
- Misses        734      740       +6     

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