Export sqlite3_trace_v2() to wasm and use it to ensure that the new per-VFS post...

Export sqlite3_trace_v2() to wasm and use it to ensure that the new per-VFS post-open SQL support in the DB ctor works. Default opfs vfs to journal_mode=truncate, as it's faster in that mode. Add 't' DB open-mode flag to enable SQL tracing to console.log().

FossilOrigin-Name: 508f7f6d63e52f61fae5abe817579a4e130fa7fbd18733d741d521a5bdabb7ce