Add preferFallback

[0xfornax]

Allow the user to specify if they want to offload tasks to the fallback to prioritize the main client for validation

Closes #319

[github-actions]

Coverage Report

[github-actions]

Merging this branch will increase overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/rocket-pool/smartnode/rocketpool-cli/service/config	0.00% (ø)
github.com/rocket-pool/smartnode/shared/services	0.47% (+0.22%)	👍
github.com/rocket-pool/smartnode/shared/services/config	6.28% (+0.08%)	👍

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/rocket-pool/smartnode/rocketpool-cli/service/config/settings-fallback.go	0.00% (ø)	2338 (+185)	0	2338 (+185)
github.com/rocket-pool/smartnode/rocketpool-cli/service/config/settings-native-fallback.go	0.00% (ø)	2030 (+162)	0	2030 (+162)
github.com/rocket-pool/smartnode/shared/services/bc-manager.go	0.59% (+0.59%)	5616 (-679)	33 (+33)	5583 (-712)	👍
github.com/rocket-pool/smartnode/shared/services/client-order.go	7.34% (+7.34%)	804 (+804)	59 (+59)	745 (+745)	👍
github.com/rocket-pool/smartnode/shared/services/config/rocket-pool-config.go	5.92% (+0.13%)	23992	1421 (+32)	22571 (-32)	👍
github.com/rocket-pool/smartnode/shared/services/ec-manager.go	0.25% (+0.25%)	7274 (+1)	18 (+18)	7256 (-17)	👍

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/rocket-pool/smartnode/shared/services/bc-manager_routing_test.go
• github.com/rocket-pool/smartnode/shared/services/client-order_test.go
• github.com/rocket-pool/smartnode/shared/services/config/prefer_fallback_test.go