Consider reducing the time taken to check for LUAZIP signatures on load

[rdw-software]

The startup times are currently longer than they need to be, as the runtime checks for LUAZIP signatures = 50ms added on Linux, even for a simple hello world app. This delay is largely because of several file system accesses, and reading the entire executable into memory via C-API bindings. Not a priority right now, as the runtime is currently much heavier than it should be.

Review afterwards.

TBD:

• Does it still take significant time to check for LUAZIP apps when the binary size is reduced?
• Does it take significant time to prepare temp dirs etc for DLL/SO extraction via fs_mkstemp?
• If so, would moving to FFI bindings for libuv help (might avoid the extra string copy)?
• Can shorten access time somehow? Maybe use env var to skip check, or seek to the end and peek at the signature?
• How significant are the differences between HDDs/SSD/NVMe and Linux/macOS/Windows?
• What performance goal should actually be targeted? Compare to other runtimes/LJ/PUC?