This commit adds support for stack traces in "deno_core".
Implementation of "Display" trait for "JsError" has been updated
and in consequence "deno_core::js_check" became obsolete and
removed.
- remove "CliState.workers" and "CliState.next_worker_id", instead
store them on "OpState" using type aliases.
- remove "CliState.global_timer" and "CliState.start_time", instead
store them on "OpState" using type aliases.
- remove "CliState.is_internal", instead pass it to Worker::new
- move "CliState::permissions" to "OpState"
- move "CliState::main_module" to "OpState"
- move "CliState::global_state" to "OpState"
- move "CliState::check_unstable()" to "GlobalState"
- change "cli_state()" to "global_state()"
- change "deno_core::ModuleLoader" trait to pass "OpState" to callbacks
- rename "CliState" to "CliModuleLoader"
