fix: override config values use viper

[yiweichi]

Purpose or design rationale of this PR

This PR aims to solve the bug when trying to override private key fields like gas_oracle_sender_private_key , commit_sender_private_key.
For now, the way we override config fields is based on the tag of JSON marshaller, but the real tag of those private keys are json:"-", so here I propose to handle it specifically as a private key when the tag is -.
Didn't use Viper because seems that will involve quite amount of code changes.

PR title

Your PR title must follow conventional commits (as we are doing squash merge for each PR), so it must start with one of the following types:

• fix: A bug fix

Deployment tag versioning

Has tag in common/version.go been updated or have you added bump-version label to this PR?

• Yes

Breaking change label

Does this PR have the breaking-change label?

• No, this PR is not a breaking change

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 56.62651% with 36 lines in your changes missing coverage. Please review.

Project coverage is 51.61%. Comparing base (a528103) to head (93f5379).

Files	Patch %	Lines
rollup/internal/controller/relayer/l2_relayer.go	47.22%	14 Missing and 5 partials ⚠️
rollup/internal/config/config.go	68.29%	8 Missing and 5 partials ⚠️
rollup/internal/controller/relayer/l1_relayer.go	33.33%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1502      +/-   ##
===========================================
- Coverage    51.71%   51.61%   -0.10%     
===========================================
  Files          156      155       -1     
  Lines        12763    12771       +8     
===========================================
- Hits          6600     6592       -8     
- Misses        5595     5606      +11     
- Partials       568      573       +5     

Flag	Coverage Δ
rollup	55.37% <56.62%> (-0.29%)	⬇️

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[georgehao]

Suggestion: use viper #1492 to replace the current implementation

[colinlyguo]

Suggestion: use viper #1492 to replace the current implementation

looks like the change is significant. @yiweichi what's the major part of code change? e.g. the self-implementing marshaling/unmarshaling private key part?

[yiweichi]

Suggestion: use viper #1492 to replace the current implementation

looks like the change is significant. @yiweichi what's the major part of code change? e.g. the self-implementing marshaling/unmarshaling private key part?

Yes, the major part would be marshaling/unmarshaling private key part.

[colinlyguo]

Suggestion: use viper #1492 to replace the current implementation

looks like the change is significant. @yiweichi what's the major part of code change? e.g. the self-implementing marshaling/unmarshaling private key part?

Yes, the major part would be marshaling/unmarshaling private key part.

added a pr to try it. still a bit messy though.