feat: allow 'latest' search for slots, blocks & epochs

[LuccaBitfly]

Allows this:

curl --location 'http://0.0.0.0:8081/api/i/search' \
                                                             --header 'Content-Type: application/json' \
                                                             --data '{
                                                             "input":"latest",
                                                             "types":["epoch"],
                                                             "networks":["hoodi"]
                                                         }'
{"data":[{"type":"epoch","chain_id":560048,"value":{"epoch":49055}}]}

[manuelsc]

lgtm

[manuelsc]

lgtm?