Clean up tests that need to shut down transaction status service.

[fkouteib]

Unify the wind down of transaction status service across different unit tests to ensure more consistency, and make sure all tx statuses are processed before the verification step of each test.

This change was forked from agave PR #4032 (specifically these comments here and here for context).

[mergify]

If this PR represents a change to the public RPC API:

1. Make sure it includes a complementary update to rpc-client/ (example)
2. Open a follow-up PR to update the JavaScript client @solana/web3.js (example)

Thank you for keeping the RPC clients in sync with the server API @fkouteib.

[fkouteib]

@steviez I tried to make the new function dcou, but ran into an issue with 'features' not allowed in 'svm/examples' toml file, which would be needed in addition to adding solana-rpc as a dev dependency. So I left it out for now.

[steviez]

@steviez I tried to make the new function dcou, but ran into an issue with 'features' not allowed in 'svm/examples' toml file, which would be needed in addition to adding solana-rpc as a dev dependency. So I left it out for now.

That is surprising to me. I don't see solana-rpc as a dependency listed here:
https://github.com/anza-xyz/agave/blob/master/svm/examples/Cargo.toml

It looks like you force-pushed and blew away your old commits so I can't see what you had. Did you see that failure reported in CI or during local build ?

[fkouteib]

Did you see that failure reported in CI or during local build ?

feature not allowed was on a local build. But it appears that was more of a skill issue on my part...I think we are good to go with the latest patch for making it dcou (asuming it clears CI). Thx for quick review and response.

[bw-solana]

Left a few nits

[bw-solana]

LGTM