[WIP] Update Lightning device TOML files to the new schema

[astralcai]

Context:

This PR is part of the new device capabilities initiative to improve feature parity across the ecosystem. See this ADR for more context. A new TOML schema has been defined, and the relevant module implemented in PennyLane:

• [New Device Capabilities] Implement the DeviceCapabilities data class and the TOML module. pennylane#6407
• [New Device Capabilities] Add capabilities to the device API pennylane#6433.

As well as updates made to Catalyst:

• [WIP] Update Catalyst to use the toml module in PennyLane catalyst#1275

Description of the Change:

• Updates lightning_qubit.toml, lightning_kokkos.toml, lightning_gpu.toml to the new schema
• Removes _operations and _observables from LightningQubit, LightningKokkos, and LightningGPU as they are now available via Device.capabilities that is loaded from the TOML file.

Benefits:

A step towards feature parity across the ecosystem.

Possible Drawbacks:

• Per discussions when the ADR was developed, operator.gates.decomp and operator.gates.matrix are removed, and the TOML file no longer prescribes to the framework how an operator should be handled. To ensure consistency of behaviour, this information is temporarily moved to a _to_matrix_ops class property to be used by Catalyst, until we have better support for customizable multi-pathway decompositions.

Related GitHub Issues:

[sc-71729]

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit .github/CHANGELOG.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[codecov]

Codecov Report

Attention: Patch coverage is 59.09091% with 9 lines in your changes missing coverage. Please review.

Project coverage is 28.46%. Comparing base (b491a37) to head (3e9f732).

Files with missing lines	Patch %	Lines
pennylane_lightning/lightning_gpu/lightning_gpu.py	57.14%	3 Missing ⚠️
...ane_lightning/lightning_kokkos/lightning_kokkos.py	57.14%	3 Missing ⚠️
...ylane_lightning/lightning_qubit/lightning_qubit.py	57.14%	3 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (b491a37) and HEAD (3e9f732). Click for more details.

HEAD has 34 uploads less than BASE

Flag	BASE (b491a37)	HEAD (3e9f732)
	38	4

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #988       +/-   ##
===========================================
- Coverage   97.97%   28.46%   -69.51%     
===========================================
  Files         221       28      -193     
  Lines       33726     2508    -31218     
===========================================
- Hits        33043      714    -32329     
- Misses        683     1794     +1111     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[astralcai]

TODO: revert this