Quick unit tests

[alexkuz]

The idea here is to have (some) unit tests use minimum dependencies so that it can be quickly compiled and run.

• packages added: global, logger, js_ast, with corresponding stubs for tests;
• added make quick-tests command for a set of unit tests (see src/__quick_tests.zig);
• some not-so-quick tests are in src/__all_quick_tests.zig;
• refactoring:
  • __global.zig removed, Global struct moved to global.zig;
  • UpdateRequest moved out from install.zig;
  • all allocators moved to src/allocators/, allocators.zig renamed to data_structures.zig (not directly related to tests, I just find it less confusing, can revert this though);
  • some global utility functions moved to global_utils.zig;
• bugs fixed:
  • SizeFormatter will print 0.51 KB instead of 1 KB for fmt.size(513) (special thanks to Zig anonymous struct literal);
  • indexOfNotChar will find a char (that's not equal to provided) as intended;
• added tests for:
  • SizeFormatter
  • range
  • copy
  • scoped package test for UpdateRequests.parse
• avoid using brew --prefix <FORMULA> on MacOS, it's very slow.