Merge tm_workspace_find() and tm_workspace_find_scoped()

Merge tm_workspace_find() and tm_workspace_find_scoped()

They are basically identical except:

1. _scoped() compares scope in addition
2. _scoped() is missing the C/CPP tag compatibility part
3. _scoped() allows returning just single result (unused)
4. _scoped() allows not searching in global tags (unused)

Since we now always put lang also under tag->lang, the match_langs()
function is not necessary.

Extend the add_filtered_tags() (and rename it to fill_find_tags_array()) to
perform the tm_tags_find(), compare the scope and add scope
as parameter of tm_workspace_find() and eliminate tm_workspace_find_scoped()
completely.