Fixes: #65830

Two argument-validation gaps in node:sqlite, both reachable from a single call with no callbacks or timing involved.

backup() reinterprets any object as a DatabaseSync*

Backup() checked only args[0]->IsObject() before ASSIGN_OR_RETURN_UNWRAP. Passing a plain object crashed; passing a different BaseObject subclass found a valid pointer in the internal field and read IsOpen() and connection_ at the wrong offsets:

This is the only one of the unwrap sites in src/node_sqlite.cc that takes a value out of args[...]; the rest use args.This() or an interceptor holder, both already covered by V8's signature check. DatabaseSync was the one class in the file with no constructor template stored on the Environment, so Backup() had nothing to test against. This adds the Environment slot and DatabaseSync::GetConstructorTemplate() alongside the ones StatementSync, StatementSyncIterator, and Session already have, and checks HasInstance() before unwrapping.

The error message changes from The "sourceDb" argument must be an object. to The "sourceDb" argument must be an instance of DatabaseSync., matching what the docs already specify for the parameter.

ValidateDatabasePath() aborts on a duck-typed URL

Any object with a string href is treated as a URL, and the parse result was asserted rather than checked, so new DatabaseSync({ href: 'zzz' }) and backup(db, { href: 'zzz' }) hit CHECK(ada::can_parse(location)) and aborted. An unparseable href now falls through to the same ERR_INVALID_ARG_TYPE that other non-URL objects get.

While in that branch: a throwing href getter had its exception discarded and replaced by ERR_INVALID_ARG_TYPE. It now propagates.

Moved code

SetSideEffectFreeGetter() moved up to the top of the file so DatabaseSync::GetConstructorTemplate() can use it. The body is unchanged.

Validation

All nine repro cases now throw TypeErrors. parallel/test-sqlite*, parallel/test-webstorage*, and parallel/test-permission-sqlite-load-extension pass, plus a check that a real URL path, Symbol.for('sqlite-type'), and backup() on a DatabaseSync subclass still behave as before.