Unified approach for printing a log id

[Zepheus]

Log IDs are printed to the log in a huge number of different styles, making it hard to search. All of these occur:

• log %lu
• logid %lu
• log_id %lu
• Log %lu
• Logid %lu
• LogID %lu
• log:%lu (no space)
• log_:%lu
• Log:%lu
• log: %lu (with space)
• Log: %lu
• LogID: %lu
• %lue%un%u (log ID with lsn, e.g. "42e420n1337")

Would be nice to codemod all of these to a single style, e.g. "log:%lu". We don't care which particular style wins, only that it be easily searchable.

• Maybe add logid_to_string() similar to lsn_to_string()? That would be slower because of the allocation in std::string
• Maybe have a macro similar to PRId64?
• Add a lint rule for things like "log %lu", "log: %lu" etc?

Probably also unify the style of log+lsn, e.g. to "log:42-e420n1337".

Until then, here's a regex to search for log 42: [Ll]og_?([Ii][Dd])?:? ?42\b|\b42e