[Configuration] Utilize viper for configuration management

[okdas]

Objective

As we are introducing cobra library to manage CLI arguments/flags (in scope of #112), it makes sense to also utilize viper - library from the same maintainers with tight integration with cobra - to provide an interface for flexible configuration. This would simplify deployments in container environments significantly, and is an existing pattern in many blockchain clients.

Origin Document

One particular example when we first encountered a need in this is during Pocket Operator PoC - https://www.youtube.com/watch?v=Tf9Qtr1gi3U - for postgres credential configuration.

Goals

• An ability to override configuration parameters via CLI arguments and/or via environment variables
• Configuration file(s) are managed via viper.

Deliverable

• An interface to change configuration parameters (that were originally set either as default value, or from configuration file) with CLI argument or environment variable/

General issue deliverables

• Update the appropriate CHANGELOG
• Update any relevant READMEs (local and/or global)
• Update any relevant global documentation & references
• If applicable, update the source code tree explanation
• If applicable, add or update a state, sequence or flowchart diagram using mermaid

[Optional] Testing Methodology

• TBD
• All tests: make test_all
• LocalNet: verify a LocalNet is still functioning correctly by following the instructions at docs/development/README.md

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Creator: @okdas
Co-Owners: TBD

[okdas]

Blocked by #112

[Olshansk]

@deblasis Can we say this is done?

[deblasis]

@deblasis Can we say this is done?

Correct