Add integration tests for sonictool.

[LuisPH3]

This PR is part of https://github.com/Fantom-foundation/sonic-admin/issues/90

During the changes introduced to capture and handle every error in the codebase, sonictool is modified with new error paths; caused by error handling from previously ignored errors.
This PR adds automated testing for the sonictool subcommands, checking that execution of such is not compromised by the introduction of new error checks.

This PR introduces two changes outside of the test:

• sonictool uses now UserPrompt for all terminal input, to facilitate testing. A proxy re-export of ethereum's UserPrompt is introduced to enable stdin redirect and mocking.
• Non-closed network stack open during sonictool execution is now closed. Otherwise, tests introduced cannot reuse database within the same process.
• New command line argument to change the db checkpoint generation interval, enabling to test sonictool heal command in a reasonable execution time.

[facuMH]

awesome work !!!