Bunch of fixes.

Fixed a few essential bugs.

• (cache_until mechanism): The roles of waiting nodes and notifier nodes
  in cache_until mechanism are in reverse. Fixed.
• (Event sources resetting): Event sources are not correctly reset during
  task resetting. Fixed.
• (Events resetting): Events may be triggered mistakenly by the stale
  emulator status owing to the delay of emulator. Fixed.

Fixed minor bugs.

• (Requirements of Gymnasium and dm-env): Gymnasium and dm-env are marked
  as optional dependencies, however, they are imported in the wrappers module
  as required sections. Fixed.
• (Crash when meeting unseen special tokens): The old behavior will crash
  when meeting special tokens from the tokenizer. Now the new behavior is to
  ignore them directly.

Migrated logging system from absl to the embedded logging module.
Updated the template toolkit to enable non-automatic concatenation of
sub-task commands.

v4.0

• Added new action and observation type of ADB
• Enabled input of common UTF-8 strings for TEXT action
• Enabled fuzzy match method for screen text events. Enabled triggering
  threshold for fuzzy match modes.
• Migrated from dm_env to android_env.interfaces to distinguish
  successful, failed, and truncated episode ends. Updated episode end events
  to control its triggering in the task definition file more conviniently.
• Added cache_until field for event slots to correctly trigger an AND
  node whose sub-events are expected to be triggered simultaneously. Now an
  activatated event can be cached temporarily until another triggered event
  clears it.
• Added null_listener for target-less event nodes.
• Applied image compression in RemoteSimulator.
• Migrated from gym to gymnasium.
• Updates to VhIoWrapper and TapActionWrapper
• Minor updates to annotation tool.

v3.6

• Updated function to load a remote simulator to enable providing the remote
  resources with a different path with the path of the local task definition
  file.
• Updated task template toolkit, added new slot modifiers and sytaxes for
  task config file.
• Fixed known bugs.

Virtually enabled all the functions.

Including:

1. remote simulator
2. annotation tool
3. VhIoWrapper & TapActionWrapper
4. ResponseEvent