Reformat `feature.name` and reintorudce `data` and `plot()` for `CompoundFeature`s

[AhmetNSimsek]

• See #417 for the conversation on feature names.
• Averaged data and averaged graphs decided to be added in the dev meeting on 22.02.2024

Please use https://github.com/FZJ-INM1-BDA/siibra-configurations/tree/use_v04_feature_ids for configuration to test.

[xgui3783]

note: waiting on me (@xgui3783 ) to create a preview viewer/api instance

[xgui3783]

additional regression not covered by tests

some features now have duplicated ids

sample code (tested for 35585fe3eb852335490737a476be49e315f16395 ):

import siibra

siibra.cache.clear()

region = siibra.get_region("cortical layer", "1 left")

f, = siibra.features.get(region, "cell density profile")
print(len([_ for _ in f]), len({_.id for _ in f})) # prints 5 3

[xgui3783]

@AhmetNSimsek are the new commits meant to address https://github.com/FZJ-INM1-BDA/siibra-python/pull/568#issuecomment-1966356183 ?

[AhmetNSimsek]

@AhmetNSimsek are the new commits meant to address #568 (comment) ?

Indeed! I forgot to ping you, sorry.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 46.15385% with 63 lines in your changes are missing coverage. Please review.

Project coverage is 51.64%. Comparing base (5a0e6b3) to head (8da694f). Report is 492 commits behind head on main.

Files	Patch %	Lines
siibra/features/tabular/cortical_profile.py	40.00%	24 Missing :warning:
siibra/features/feature.py	40.74%	16 Missing :warning:
...a/features/tabular/regional_timeseries_activity.py	45.45%	12 Missing :warning:
...bra/features/connectivity/regional_connectivity.py	23.07%	10 Missing :warning:
...a/features/connectivity/functional_connectivity.py	0.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #568 +/- ## =========================================== + Coverage 36.81% 51.64% +14.82% =========================================== Files 61 74 +13 Lines 5421 7012 +1591 =========================================== + Hits 1996 3621 +1625 + Misses 3425 3391 -34 ```

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