Fixup onefuzz-task dependencies

[Porges]

Both the bin and lib for onefuzz-task include the same modules, which means some code is being compiled twice, and this leads to confusing errors if you update the bin code and not the lib code (e.g. adding new modules or something similar).

Instead, make the bin code depend on the lib code.

Also remove extern crate and macro_use, which are an older way of doing things. Macros are simply imported now.

[codecov-commenter]

Codecov Report

Merging #3552 (3e85571) into main (003c9ac) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #3552   +/-   ##
=======================================
  Coverage   38.97%   38.97%           
=======================================
  Files         301      301           
  Lines       36848    36848           
=======================================
  Hits        14363    14363           
  Misses      22485    22485           

Files	Coverage Δ
src/agent/onefuzz-task/src/check_for_update.rs	0.00% <ø> (ø)
src/agent/onefuzz-task/src/managed/cmd.rs	0.00% <0.00%> (ø)
src/agent/onefuzz-task/src/main.rs	0.00% <0.00%> (ø)