refactor(zetaclient): improve some general structure of the codebase

[lumtis]

Description

Add some improvement in the codebase following this issue: #2026

[github-actions]

!!!WARNING!!!
nosec detected in the following files: zetaclient/bitcoin/bitcoin_client.go, zetaclient/bitcoin/fee.go, zetaclient/bitcoin/inbound_tracker.go, zetaclient/config/config_chain.go, zetaclient/evm/evm_client.go, zetaclient/keys/keys_test.go, zetaclient/tss/tss_signer.go

Be very careful about using #nosec in code. It can be a quick way to suppress security warnings and move forward with development, it should be employed with caution. Suppressing warnings with #nosec can hide potentially serious vulnerabilities. Only use #nosec when you're absolutely certain that the security issue is either a false positive or has been mitigated in another way.

Only suppress a single rule (or a specific set of rules) within a section of code, while continuing to scan for other problems. To do this, you can list the rule(s) to be suppressed within the #nosec annotation, e.g: /* #nosec G401 */ or //#nosec G201 G202 G203
Broad #nosec annotations should be avoided, as they can hide other vulnerabilities. The CI will block you from merging this PR until you remove #nosec annotations that do not target specific rules.

Pay extra attention to the way #nosec is being used in the files listed above.

[codecov]

Codecov Report

Attention: Patch coverage is 15.60380% with 622 lines in your changes are missing coverage. Please review.

Project coverage is 70.17%. Comparing base (55c65e0) to head (b03631a).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2032      +/-   ##
===========================================
- Coverage    70.70%   70.17%   -0.54%     
===========================================
  Files          252      249       -3     
  Lines        14052    14135      +83     
===========================================
- Hits          9936     9919      -17     
- Misses        3656     3758     +102     
+ Partials       460      458       -2     

Files	Coverage Δ
zetaclient/bitcoin/fee.go	89.89% <ø> (ø)
zetaclient/bitcoin/inbound_tracker.go	0.00% <ø> (ø)
zetaclient/bitcoin/tx_script.go	93.10% <ø> (ø)
zetaclient/config/config.go	0.00% <ø> (ø)
zetaclient/config/config_chain.go	0.00% <ø> (ø)
zetaclient/core_context/zeta_core_context.go	90.82% <ø> (ø)
zetaclient/evm/inbounds.go	69.32% <ø> (ø)
zetaclient/interfaces/signer.go	0.00% <ø> (ø)
zetaclient/metrics/burn_rate.go	79.16% <ø> (ø)
zetaclient/supplychecker/validate.go	100.00% <100.00%> (ø)
... and 13 more

... and 4 files with indirect coverage changes

[ws4charlie]

looks nice. Left a few minor comments.

[skosito]

some smaller comments, looks good