Automatically install npm packages when running a script in Bun's runtime (#1459)

* Update bundler.zig

* WIP

* Update README.md

* Update README.md

* wip

* Support running scripts without package.json

* Add `--no-auto-install` and `--prefer-offline` flags

* WIP

* wip

* Update headers-handwritten.h

* WIP

* Build fixes

* Fix UAF

* Update install.zig

* Must call .allocate()

* Micro-optimization: only call .timestamp() once per tick when installing packages

* Support progress bar

* Extend the timestamp for package staleness checks to 1 day

* Add `--prefer-latest`, `-i` CLI Flags

* Fix crash

* Support line text manually being set on an Error instance

* Add a few more fields for error messages

* Fix bug when counting 8 character strings in string builder

* Implement error handling for automatic package installs!

* Fix crash

* Make it say module when there's a slash

* Update module_loader.zig

* Ban dependency versions in import specifiers when a package.json is present

* Remove unused field

* Update README.md

* Update README.md

* Update README.md

* Update README.md

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

src/cli/test_command.zig

@@ -338,6 +338,9 @@ pub const TestCommand = struct {
             }
         }
 
+        vm.is_main_thread = true;
+        JSC.VirtualMachine.is_main_thread_vm = true;
+
         var scanner = Scanner{
             .dirs_to_scan = Scanner.Fifo.init(ctx.allocator),
             .options = &vm.bundler.options,