Bump the all-julia-packages group across 6 directories with 6 updates

[shravanngoswamii]

Supersedes #173.

Same dependency bump dependabot proposed there (OrderedCollections 2.0, ADTypes 1.22.0, ForwardDiff 1.4.1, Distributions 0.25.126, Documenter 1.17.0), reopened from a plain branch instead of dependabot/julia/*.

The CI failures on #173 were a false positive of julia-runtest's force_latest_compatible_version: auto, which forces true purely by matching the branch name against dependabot/julia*/compathelper/* (see julia-actions/julia-runtest's autodetect-dependabot.jl) and then pins every [compat] entry to the top of its own sub-range independently. That produces two conflicts that don't reflect anything a real user would hit:

• OrderedCollections forced to 2.0.1 vs. DimensionalData.jl (test-only, still pins OrderedCollections = "1" upstream)
• JET forced to 0.11.x vs. PrecompileTools needing Julia 1.12, on the min/1.11 jobs

Under normal resolution (this branch), both resolve fine on their own: OrderedCollections settles at 1.8.2, JET at 0.9.20 on old Julia. Verified locally:

• Pkg.resolve() on test/Project.toml succeeds with no conflicts
• Full test suite passes (1498/1498)
• Separately dev'd AbstractPPL against OrderedCollections@2.0.0 directly (outside the DimensionalData-constrained test env) — precompiles clean, OrderedDict construction and the varname serialize/deserialize round-trip both work

Also bumped the self-referential AbstractPPL compat entries in docs/Project.toml and test/ext/*/Project.toml from 0.15.2 to 0.15.4 to match the version currently on main (they were stale from when dependabot last ran).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.14%. Comparing base (b093e7d) to head (d10da9a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #179   +/-   ##
=======================================
  Coverage   92.14%   92.14%           
=======================================
  Files          17       17           
  Lines        2100     2100           
=======================================
  Hits         1935     1935           
  Misses        165      165           

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[github-actions]

AbstractPPL.jl documentation for PR #179 is available at:
https://TuringLang.github.io/AbstractPPL.jl/previews/PR179/

[shravanngoswamii]

Tried taking OrderedCollections to 2.0 as well, but reverted it: on Julia 1.12, normal resolution legally picks DimensionalData v0.29.12 + OrderedCollections v2.0.1 together (both satisfy declared compat), and that combination crashes at precompile time in DimensionalDataStatsBase (UndefVarError: X not defined in DimensionalData.Dimensions, a stricter Julia-1.12 world-age rule tripping up DimensionalData 0.29.12's own precompile workload). Confirmed via the CI run on this PR, not just locally. So OrderedCollections stays at 1.8.1 for now — not safe to widen while test/Project.toml still allows the 0.29 line of DimensionalData. Rest of the bump (ADTypes, ForwardDiff, Distributions, Documenter, AbstractPPL self-compat) unaffected.