os: implement waitable management.

This implements waitable management for Events (and
implements Events). It also refactors PM to use new
Event/Waitable semantics, and also adds STS_ASSERT
as a macro for asserting a boolean expression. The
rest of stratosphere has been refactored to use
STS_ASSERT whenever possible.

stratosphere/boot/source/i2c/i2c_command_list.hpp

@@ -43,9 +43,7 @@ namespace sts::i2c {
             size_t cur_index = 0;
         public:
             CommandListFormatter(void *cmd_list, size_t cmd_list_size) : cmd_list(static_cast<u8 *>(cmd_list)), cmd_list_size(cmd_list_size) {
-                if (cmd_list_size > MaxCommandListSize) {
-                    std::abort();
-                }
+                STS_ASSERT(cmd_list_size <= MaxCommandListSize);
             }
             ~CommandListFormatter() {
                 this->cmd_list = nullptr;