Reduce generics (C, W, WIT_LEN), reduce examples (#194)

Enhances developer experience a bit by,

- Generics,
  - Removes the const generics `C`, `W`, `WIT_LEN`.
  - Renames `C` to `KAPPA` (number of rows in the Ajtai matrix);
- Renames `W` to `N` (number of columns in the Ajtai matrix, decomposed
witness size).
- Examples,
  - Reduces the similar examples to a single one using Goldilocks;
  - Removes stark-specific parameters.

Author: v0-e

crates/latticefold/benches/config.toml

@@ -28,7 +28,7 @@ pub struct Env {
     pub e2e: bool,
     pub x_len: Option<usize>,
     pub kappa: Option<usize>,
-    pub w: Option<usize>,
+    pub n: Option<usize>,
     pub wit_len: Option<usize>,
     pub b: Option<u128>,
     pub l: Option<usize>,
@@ -87,7 +87,7 @@ lazy_static! {
             e2e,
             x_len: get_env_var("X_LEN"),
             kappa: get_env_var("KAPPA"),
-            w: get_env_var("W"),
+            n: get_env_var("N"),
             wit_len: get_env_var("WIT_LEN"),
             b: get_env_var("B"),
             l: get_env_var("L"),