feat!: add support of loading dataset metadata

[ktro2828]

What

This PR adds support of loading T4 dataset metadata including dataset ID and version.
Note that the parameter of initializing Tier4 class is changed from this PR as below.

Now, we have the following dataset structure:

dataset1
└── 0
   ├── annotation
   ├── data
   ...

Then you can initialize

>>> from t4_devkit import Tier4

>>> t4 = Tier4("dataset1")
>>> t4.data_root
"dataset1/0"
>>> t4.dataset_id
"dataset1"
>>> t4.version
"0"

It is also allowed to load T4 dataset without version directory, then version returns None:

dataset2
├── annotation
├── data
 ...

>>> from t4_devkit import Tier4

>>> t4 = Tier4("dataset1")
>>> t4.data_root
"dataset1"
>>> t4.dataset_id
"dataset1"
>>> t4.version
None

[github-actions]

☂️ Python Coverage

current status: ❌

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
2351	1588	68%	50%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
t4_devkit/common/sanity.py	0%	🔴
t4_devkit/helper/rendering.py	13%	🔴
t4_devkit/tier4.py	17%	🔴
TOTAL	10%	🔴

updated for commit: 270421c by action🐍