rename project to MultiforaDB

Prose and benchmark tables use MultiforaDB; the binary, the CLI usage
line, the log-message prefix and the default database file use
multiforadb.

Two consequences worth noting:

- build.zig.zon's fingerprint is derived from the package name, so it
  had to change with it (Zig refuses to build otherwise). A consumer
  pinning this package by fingerprint needs updating.
- the default --db path is now multiforadb.log, and getCmdLineOpts
  reports it as dbpath. An existing mongo-lite.log has to be passed
  explicitly with --db.

The e2e harness abbreviated the old name as ML_; that is now MFDB_,
including the documented ML_BIN override (MFDB_BIN) and the scratch
file names. MD_ (mongod) is untouched.

compare-run.sh spawned the server by absolute path under a
sandbox/mongo-lite directory that no longer exists; that block already
runs from tests/e2e, so it uses a relative path now.

The archived reports under tests/e2e/results/ keep the old name: they
record what the old binary measured.

tests/e2e/package.json

@@ -1,7 +1,7 @@
 {
   "name": "e2e",
   "version": "1.0.0",
-  "description": "These exercise mongo-lite from a real driver over TCP: full CRUD, query operators, aggregation, error codes, concurrent clients, and crash recovery.",
+  "description": "These exercise multiforadb from a real driver over TCP: full CRUD, query operators, aggregation, error codes, concurrent clients, and crash recovery.",
   "main": "e2e.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1"