refactor(zetaclient): use keyring backend file for hotkey

[lumtis]

Description

• Remove the password from the ZetaClient config
• Add option KeyringBackend in ZetaClient config for the keyring backend used for the key
• Add the File keyring backend for hot key for encryption
• Use Keyring Backend file in the smoketests

When using keyring backend file, the password must be provided through the env var HOTKEY_PASSWORD

export HOTKEY_PASSWORD=foobarfoo
zetaclientd ... --keyring-backend file

Closes: #1278

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Include instructions and any relevant details so others can reproduce.

• Tested CCTX in localnet
• Tested in development environment
• Go unit tests
• Go integration tests
• Tested via GitHub Actions

Checklist:

• I have added unit tests that prove my fix feature works

[github-actions]

!!!WARNING!!!
nosec detected in the following files: contrib/localnet/orchestrator/smoketest/main.go

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[lumtis]

I will wait on a review from @kevinssgh before merging if you can have a look sometime. Thanks