Reenable missing AddTracker tests and mock header/proof functionality for AddTracker and AddBlockHeader

[lumtis]

#1872 currently comment out some of the tracker tests as those doesn't work when Goerli RPC is no longer supported

We should add test back using static data instead of using RPCs. However, since block/header verification shouldn't be a concern for adding tracker, this is a functionality performed by the proof verification system itself, this functionality should be mocked for these tests.

This is the same for MsgAddBlockHeader in observer. The actual logic of adding the block header should be mocked in the observer module.

Depending on #1491
once the new module is implemented we can define mocks for add header and proof verification