client: Fix unclean shutdown scenario where SIGINT may come before client fully started

[g11tech]

It may take client a little while to fully start and bootstrap its services (especially if there are pending blocks to be executed). If SIGINT/CTRL + C comes before that, client may end up in an unclean shutdown

This PR hooks up shutdown handler as soon as client is started, and also makes sure client is properly started before initiating a clean shutdown:

PS: Build on top of client memory optimizations PR and is pointing to that branch

• Client Memory Optimizations #2675

So pls rebase and merge afterwards 2675 is merged and with the base branch of this PR updated to develop-v7

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop-v7@9b85ff1). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

Flag	Coverage Δ
block	90.30% <0.00%> (?)
blockchain	90.45% <0.00%> (?)
client	86.88% <0.00%> (?)
common	95.76% <0.00%> (?)
devp2p	91.89% <0.00%> (?)
ethash	∅ <0.00%> (?)
evm	79.35% <0.00%> (?)
statemanager	88.53% <0.00%> (?)
trie	89.68% <0.00%> (?)
tx	95.50% <0.00%> (?)
util	81.34% <0.00%> (?)
vm	84.39% <0.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

[holgerd77]

Have admin merged 2675, thought this would ease the process, PR here is still off with commits though, might need an update.

[g11tech]

Have admin merged 2675, thought this would ease the process, PR here is still off with commits though, might need an update.

yea noticed 🙂 , updated

[holgerd77]

Great structural approvement! 🎉

Will approve and merge.