Standardize the output format of qml.specs

[jzaia18]

Context:
qml.specs makes very few guarantees on the shape of its output. This PR aims to make a single unified out type for qml.specs, which contains all of (and only) the information needed for circuit inspection.

Description of the Change:

• Introduces new SpecsResources and CircuitSpecs classes
• Refactors various specs functions throughout PennyLane to make use of the new classes
• Updates _count_resources to use the Catalyst-style resource names for multi-controlled gates. e.g. a 10-controlled IsingXX is now shown as 10C(IsingXX) and no longer just C(IsingXX). This matches how resources are counted in Catalyst.

Benefits:
Cleaner and more consistent specs returns.

Happens to also fix #8048

Possible Drawbacks:
Introduces another "resources" object into PennyLane. A followup PR should restructure these PRs such that all of them inherit from a common base class.

Removes some information which used to be included in qml.specs, such as num_observables (now migrated into the resources' measurements) or various gradient information.

Related GitHub Issues:
[sc-104965]
#8048

[github-actions]

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Please edit doc/releases/changelog-dev.md with:

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.37%. Comparing base (0e7bedd) to head (7e3809b).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8713      +/-   ##
==========================================
- Coverage   99.37%   99.37%   -0.01%     
==========================================
  Files         589      589              
  Lines       62830    62929      +99     
==========================================
+ Hits        62437    62534      +97     
- Misses        393      395       +2     

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[jzaia18]

Just a heads up that I'll also need reviews on this follow-up PR which fixes the specs integration tests in Catalyst: PennyLaneAI/catalyst#2255 . These tests will begin to fail as soon as the changes from this PR are used with Catalyst (requires a change to the manual pin)

[albi3ro]

So excited to have this in! I've actually wanted something like this for a while, so quite happy to have something like this now.

[mudit2812]

Looks great @jzaia18 .

Introduces another "resources" object into PennyLane. A followup PR should restructure these PRs such that all of them inherit from a common base class.

Is there already a story for this? If not, could you please add one?

[jzaia18]

Is there already a story for this? If not, could you please add one?

Not sure about a story, but I think there's a whole epic for it planned for Q1, it's in the technical roadmap