[EVM-370] Added --insecure flag to both ibft and polybft

[ZeljkoBenovic]

Description

When initializing the chain and using a local storage, private keys are stored as a plaintext format by default, in a local folder the operator has defined during the secrets init or polybft-secrets init stage.

This PR adds the --insecure flag as mandatory in order to store private keys unencrypted.
If the operator tries to run secrets init or polybft-secrets init command without --insecure flag, the error use a secrets backend, or supply an --insecure flag... will be presented.
When --insecure flag is used for storing the secrets locally, the following warning will be presented:
[WARNING: INSECURE LOCAL SECRETS - SHOULD NOT BE RUN IN PRODUCTION]
as storing secrets using this method, presents a high security risk and should not be used in production environments.

Changes include

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels
• I have updated the official documentation
• I have added sufficient documentation in code

Testing

• I have tested this code with the official test suite
• I have tested this code manually

Manual tests

Run secrets init --data-dir <folder> or polybft-secrets init --data-dir <folder>- it should fail with an error use a secrets backend, or supply an --insecure flag....
Run secrets init --data-dir <folder> --insecure or polybft-secrets init --data-dir <folder> --insecure- it should succeed with a warning [WARNING: INSECURE LOCAL SECRETS - SHOULD NOT BE RUN IN PRODUCTION]

Additional comments

Fixes EVM-370
Fixes EDGE-1024

[Stefan-Ethernal]

LGTM

[codecov]

Codecov Report

Merging #1182 (18af72b) into feature/v3-parity (576f435) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@                  Coverage Diff                  @@
##           feature/v3-parity    #1182      +/-   ##
=====================================================
- Coverage              54.84%   54.80%   -0.04%     
=====================================================
  Files                    176      176              
  Lines                  23519    23519              
=====================================================
- Hits                   12898    12889       -9     
- Misses                  9590     9598       +8     
- Partials                1031     1032       +1     

Impacted Files	Coverage Δ
network/server_discovery.go	74.53% <0.00%> (-7.46%)	⬇️
syncer/client.go	63.20% <0.00%> (+1.41%)	⬆️

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