Why

I wanted to clear the way for #8242 to be landed (or not). I noticed that web support doesn't look like it should work and that it isn't tested anywhere.

How

• added SQLite test suite to set run on web
• changed the way we fetch values in test suite from using ._array[0] to .item(0)
• added explanations in SQLite.types.ts about why we may need a copy of @types/websql
• added Window declaration to types declarations
• removed @types/websql dependency as it's not even importable
• fixed web counterpart — SQLite.web.ts — by fixing the method header and gracefully handling situation where openDatabase is not available (I think).

Test Plan

Test suite passes.