feat(perf): ship ModernFix dynamic_resources, add Flerovium and Iris Flywheel Compat

Bench (proxy 9900X/7800XT, see analysis/client-perf/RESULTS-proxy.md):
- ModernFix mixin.perf.dynamic_resources=true: startup -7.6 s, S1 p99
  9.11 -> 8.48 ms, S2 1% low 236 -> 264 fps (B6). Enforced packwiz file
  because ModernFix reads it before Default Options. Missing-texture check
  waived by owner; issues to be reported from play.
- Flerovium 1.1.2 (client): mob-pen S3 p99 ~0.9 ms better (B12b).
- Iris Flywheel Compat 2.4.0 (client): with a shaderpack, Create floor
  p99 13.3 -> 4.0 ms (Flywheel instancing kept under Iris) (B12b).
Deck tier already ships DH's LOW quality preset, so no DH change.

pack.toml

@@ -6,7 +6,7 @@ pack-format = "packwiz:1.1.0"
 [index]
 file = "index.toml"
 hash-format = "sha256"
-hash = "a541a5c87ef6ab98ce6c87526cc192e19ba9cccdbf197388de1394dfb1124a8b"
+hash = "fa466ffeb5cefd0adac6b88b4ed08bb5b2fe0a138f49e9f2d6ea99b8fee70af3"
 
 [versions]
 minecraft = "1.21.1"