fix: stale error handling for unsigned extrinsics (PRO-804)

[AlastairHolmes]

No description provided.

[linear]

PRO-804 [Bug] CFE shut down on "Invalid Transaction"

When doing some bouncer testing I've managed to make the engine "crash".

Error: RPC call failed: ErrorObject { code: ServerError(1010), message: "Invalid Transaction", data: Some(RawValue("Transaction is outdated")) }
Caused by:
    RPC call failed: ErrorObject { code: ServerError(1010), message: "Invalid Transaction", data: Some(RawValue("Transaction is outdated")) }

It's referring to the unsigned extrinsic submission in particular.

In order to reproduce:

Get commit hash `08854b664121782e1b2202f4ccaf425a8779fc3a`

Run setup_vaults and setup_swaps.

Then run gaslimit_ccm.ts test. It will take a while until after some broadcast aborted things start to fail and ends up with the CFE exiting gracefully and the witnessing stops.

[codecov]

Codecov Report

Merging #4100 (39037bd) into main (b1093cd) will decrease coverage by 0%.
Report is 4 commits behind head on main.
The diff coverage is 48%.

@@          Coverage Diff          @@
##            main   #4100   +/-   ##
=====================================
- Coverage     71%     71%   -0%     
=====================================
  Files        377     377           
  Lines      59965   59974    +9     
  Branches   59965   59974    +9     
=====================================
- Hits       42722   42716    -6     
- Misses     15006   15018   +12     
- Partials    2237    2240    +3     

Files	Coverage Δ
...tate_chain_observer/client/extrinsic_api/common.rs	53% <100%> (+53%)	⬆️
.../client/extrinsic_api/signed/submission_watcher.rs	23% <ø> (-2%)	⬇️
engine/src/state_chain_observer/sc_observer/mod.rs	37% <100%> (ø)
...gine/src/state_chain_observer/sc_observer/tests.rs	88% <100%> (ø)
engine/src/state_chain_observer/client/mod.rs	17% <17%> (-<1%)	⬇️
...te_chain_observer/client/extrinsic_api/unsigned.rs	0% <0%> (ø)

... and 6 files with indirect coverage changes

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