fix: skip already queued up tx

[gosuto-inzasheru]

closes #87

ideally we would create a test that simulates the current bug, then prove that this change fixes the test

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 95.67%. Comparing base (c798d87) to head (3e69e03).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #92      +/-   ##
==========================================
- Coverage   97.07%   95.67%   -1.41%     
==========================================
  Files           2        2              
  Lines         205      208       +3     
  Branches       33       34       +1     
==========================================
  Hits          199      199              
- Misses          2        5       +3     
  Partials        4        4              

Files	Coverage Δ
src/RoboSaverVirtualModule.sol	96.19% <25.00%> (-1.60%)	⬇️

[gosuto-inzasheru]

im thinking as a quick fix for this we can, for now, adjust the _isExternalTxQueued requirement to just check for any queued tx, and thus not queue multiple txs at all

[petrovska-petro]

actually in this case i think, since what we encountered is cause shutdown is trigger on a diff completely flow than anything going thru check&perform combo, meaning the admin is triggering proactively, maybe it's simpler to check if when trying to call it, say, if queuedTx.nonce != 0 then somehow the shutdown should be prio and perhaps delete existing payload stored there, which will force to expired whatever was queued internally or otherwise, do not allow to queue shutdown when smth is already queue, but i think that shutdown should have prio over whatever is queue before internally, no?