Port a lot of DB libraries and machinery

[pbiggar]

Port DB libraries:

• add a way to specific DBs in tests
• clear DB before tests with DBs in them
• add DBs (and secrets) to global variables
• Port old DB libraries (that do nothing)
• add appropriate formats for saving Dvals, and Sql convenience functions: Sql.roundtrippableDval, etc
• implement all of UserDB.fs
• add support for DB::set_v1, DB::get_V1, DB::query_v1, DB::query_v2, DB::query_v3, DB::getAll_v1, DB::getAllWithKeys_v1, DB::getAllWithKeys_v2, DB::getExisting_v0, DB::getManyWithKeys_v0, DB::getManyWithKeys_v1, DB::getMany_v1, DB::getMany_v2, DB::getMany_v3, DB.queryWithKey_v1, DB.queryWithKey_v2, DB::queryOne_v1, DB::queryOne_v4, DB::queryOneWithKey_v1, DB::queryOneWithKey_v2, DB::getAll_v1
• add support for other functions i needed for these tests: List::sortBy_v0, Date::parse_v2, Date::<_v0, Date::>_v0, Date::<=_v0, Date::>=_v0
• implement most of SqlCompiler, including using function signatures instead of hardcoding them in the SqlCompiler

Other changes:

• show number of commented out tests in test harness
• create ExecutionState
• add secrets to canvas
• move shortcuts to own file
• move http error checking
• fix http "Not found" tests
• create function list lazily
• get test user/canvas lazily and cache it to speed up tests
• disable HTTP logging when testing
• match EVariable interpreter implementation
• fix sha1digest
• add Tablecloth.Map.merge
• support try/with in TaskOrValue (and fix fallout!)
• add Ast.fs with traversal functins
• move functions with no module name to LibNoModule.fs
• a few expansions to the F# parser (field access, toString, parsing Date.(<)
• fix randomString (and make it print only capital letters)
• error check when making error message for functions with wrong number of args
• troubleshooting info for VSCode
• make TestUtils.fs with shared test code