perf: remove void JP arguments

[hargoniX]

This PR makes the compiler removes arguments to join points that are void, avoiding a bunch of dead
stores in the bytecode and the initial C (though LLVM was surely able to optimize these away further
down the line already).

[hargoniX]

!bench

[leanprover-radar]

Benchmark results for a068019 against 36f05c4 are in! @hargoniX

• 🟥 build//instructions: +324.0M (+0.00%)

Small changes (1✅, 1🟥)

• 🟥 build/module/Lean.Compiler.LCNF.ToImpure//instructions: +337.6M (+6.26%) (reduced significance based on *//lines)
• ✅ size/all/.ir//bytes: -813kiB (-0.25%)

[mathlib-lean-pr-testing]

Mathlib CI status (docs):

• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase 36f05c4a18412c6a1699a98b283c5730eda904cb --onto cda84702e9b31165f1f83c657b532f36f34e0bd0. You can force Mathlib CI using the force-mathlib-ci label. (2026-03-04 16:31:25)

[leanprover-bot]

Reference manual CI status:

• ❗ Reference manual CI will not be attempted unless your PR branches off the nightly-with-manual branch. Try git rebase 36f05c4a18412c6a1699a98b283c5730eda904cb --onto cda84702e9b31165f1f83c657b532f36f34e0bd0. You can force reference manual CI using the force-manual-ci label. (2026-03-04 16:31:26)