Remove NodeTrait

[penelopeysm]

Instead of using NodeTrait, this PR uses AbstractParentContext.

I think the changelogs and docs explain the interesting bits. Most of the code changes are just tedium.

Closes #1052.

[codecov]

Codecov Report

❌ Patch coverage is 76.92308% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.32%. Comparing base (a8eb2e7) to head (e54d3c3).
⚠️ Report is 1 commits behind head on breaking.

Files with missing lines	Patch %	Lines
src/contexts/conditionfix.jl	79.16%	5 Missing ⚠️
src/contexts.jl	50.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           breaking    #1133      +/-   ##
============================================
- Coverage     81.48%   81.32%   -0.16%     
============================================
  Files            40       40              
  Lines          3845     3807      -38     
============================================
- Hits           3133     3096      -37     
+ Misses          712      711       -1     

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[github-actions]

Benchmark Report for Commit e54d3c3

Computer Information

Julia Version 1.11.7
Commit f2b3dbda30a (2025-09-08 12:10 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 7763 64-Core Processor
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, znver3)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)

Benchmark Results

┌───────────────────────┬───────┬─────────────┬───────────────────┬────────┬────────────────┬─────────────────┐
│                 Model │   Dim │  AD Backend │           VarInfo │ Linked │ t(eval)/t(ref) │ t(grad)/t(eval) │
├───────────────────────┼───────┼─────────────┼───────────────────┼────────┼────────────────┼─────────────────┤
│ Simple assume observe │     1 │ forwarddiff │             typed │  false │            6.8 │             1.7 │
│           Smorgasbord │   201 │ forwarddiff │             typed │  false │          759.1 │            44.9 │
│           Smorgasbord │   201 │ forwarddiff │ simple_namedtuple │   true │          425.6 │            58.1 │
│           Smorgasbord │   201 │ forwarddiff │           untyped │   true │          817.8 │            37.5 │
│           Smorgasbord │   201 │ forwarddiff │       simple_dict │   true │         6930.7 │            25.6 │
│           Smorgasbord │   201 │ forwarddiff │      typed_vector │   true │          795.0 │            42.1 │
│           Smorgasbord │   201 │ forwarddiff │    untyped_vector │   true │          823.3 │            37.4 │
│           Smorgasbord │   201 │ reversediff │             typed │   true │          941.1 │            45.2 │
│           Smorgasbord │   201 │    mooncake │             typed │   true │          751.1 │             5.9 │
│           Smorgasbord │   201 │      enzyme │             typed │   true │          936.9 │             4.0 │
│    Loop univariate 1k │  1000 │    mooncake │             typed │   true │         4019.9 │             5.9 │
│       Multivariate 1k │  1000 │    mooncake │             typed │   true │         1108.3 │             8.5 │
│   Loop univariate 10k │ 10000 │    mooncake │             typed │   true │        44096.3 │             5.4 │
│      Multivariate 10k │ 10000 │    mooncake │             typed │   true │         9338.4 │             9.7 │
│               Dynamic │    10 │    mooncake │             typed │   true │          126.7 │            12.0 │
│              Submodel │     1 │    mooncake │             typed │   true │            8.9 │             6.7 │
│                   LDA │    12 │ reversediff │             typed │   true │         1027.2 │             2.0 │
└───────────────────────┴───────┴─────────────┴───────────────────┴────────┴────────────────┴─────────────────┘

[github-actions]

DynamicPPL.jl documentation for PR #1133 is available at:
https://TuringLang.github.io/DynamicPPL.jl/previews/PR1133/

[mhauru]

LGTM, happy about the simplification.