test(bug): In TestExportImport, delete imported key, check if original exists

[jefft0]

This PR demonstrates a bug. TestExportImport creates a key named "john", uses Export to export it, then uses Import to import it into the same Keybase with the new name "john2". It checks if the address of the imported key is the same as the original key.

This PR expands TestExportImport to delete the imported "john2" then uses HasByName("john") to check if the original key still exists.

To run the test:

cd gno/tm2/pkg/crypto/keys
go test .

Expected: pass. Actual: The test fails with:

        	Error Trace:	/Users/jefft0/work/gno/gno/tm2/pkg/crypto/keys/keybase_test.go:246
        	Error:      	Should be true
        	Test:       	TestExportImport

Discussion: The Export function exports the Info struct which has the key name, in this case "john". Then Import imports the key with a new name, but does not change the Info struct. (Is this by design?) The Delete function fetches the Info struct from the database using the new name "john2", but it deletes based on the original name in the struct. This deletes the key under the original name.

Maybe Import needs to modify the Info struct with the new name before storing in the database.