always sign validator uptimes

[ceyonur]

Why this should be merged

This PR introduces recognizing, parsing and verification of ValidatorUptime messages. Verification is basically skipped and all uptime messages are signed.

How this works

This pull request introduces new functionality for verifying addressed call messages and adds corresponding tests and metrics. The main changes include adding a new verification function, updating the switch statement to handle the new message type, and adding test cases and metrics for uptime validation.

New functionality for verifying addressed call messages:

• warp/verifier_backend.go: Added a new import for messages and implemented the verifyAddressedCall function to parse and verify addressed call messages. The switch statement in the Verify function was updated to handle payload.AddressedCall messages. [1] [2] [3]

Tests for the new functionality:

• warp/verifier_backend_test.go: Added a new import for messages and implemented TestUptimeSignatures to test the verification of uptime messages. [1] [2]

Metrics for uptime validation:

• warp/verifier_stats.go: Added a new counter for uptimeValidationFail and a corresponding increment function IncUptimeValidationFail. [1] [2]

How this was tested

Added UT

How is this documented

No need