feat: Using global private environment to save secrets[INS-4715]

[cwangsmv]

Changes
Leverage global private environment to add built-in support secret management capabilities.
Add a new secret type environment key-value pair to store secret variables with the following features:

• Secret environment variables will add a vault prefix automatically to distinguish with normal environment variables. If you define a secret environment called foo, you need to input {{ vault.foo }} to use as environment variable
• Secret environment values are encrypted in the database
• Secret environment values are masked unless in environment editor/variable editor modal/using in request
• When the private environment is exported, a default placeholder string will replace its real value
• When user has rest the encryption key (aka: vault key) in other devices, all local secret environment variables will be removed

We also introduce a new term Vault Key.
Vault key is used to encrypt/decrypt secret environment variables, it is not synced to the cloud, so users need to save the key themselves.
User could reset the vault key, but this will remove local secret environments in all devices.
Add a new UI in Preferences page for management:

By default, we will save the vault key in OS native secret manager(like KeyChain in MacOS).

Tasks

• Add new UI for secret environment variables
• Secret environment variables processing logic
  • Mask value unless in editor and request
  • Encryption/Decryption logic
• Vault key UI
  • New vault key management UI in Preferences modal
  • API integration and SSE event handling
  • Vault key/hash CRUD operations
• Pre-requset & After-response support
• CLI Support

This PR relies on #8190 to merge first.