feat(tui): add failover controls

[unive3sal]

A huge commit for failover TUI and integration tests. It is mainly consist of the following parts:

• user can manually enable/disable auto-failover
• provider SHOULD ONLY selected from failover queue when failover is enable
• user can specify a provider from provider list when failover is disable (use "space" key to specify the active provider)
• user cannot specify one typical provider but set the priority in failover queue when failover is enable
  (all of the provider in queue SHOULD be marked as "✓" status)
• if (failover is disable && user does not specify a provider), then proxy cannot be activated
• if (failover is enable && failover queue is empty), then proxy cannot be activate
• failover queue should support hot updates during proxy enabled
  (but cannot remove all providers, it should always keep at least 1 provider in queue)

interactive failover TUI

add a temp window in "Providers"

when failover is disable

• user can specify ONLY 1 provider from provider list

when failover is enable

• user can update priority for each provider

E2E integration test

• It will create a sandbox to run E2E tests
• Creating some positive/negative mock providers during test

edge cases

• failover queue is empty; expectation: cannot enable proxy
• failover queue has ONLY 1 provider; expectation: ONLY use this provider in queue. even if it is down, active provider cannot be transfer
• failover queue has more than 1 provider; expectation: auto-transfer to different provider according to priority when current active provider is unavailable.
• all of the providers in queue are unavailable; expectation: cannot work normally

Fixes #19
Fixes #101
Fixes #98

[SaladDay]

merge一下main