✨ irm: add utilization utils

src/interest-rate-model/fixedUtilization.ts

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+import WAD from "../fixed-point-math/WAD.js";
+
+export default function fixedUtilization(supplied: bigint, borrowed: bigint, assets: bigint) {
+  return assets !== 0n && borrowed > supplied ? ((borrowed - supplied) * WAD - 1n) / assets + 1n : 0n;
+}

src/interest-rate-model/floatingUtilization.ts

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+import WAD from "../fixed-point-math/WAD.js";
+
+export default function floatingUtilization(assets: bigint, debt: bigint) {
+  return assets !== 0n && debt !== 0n ? (debt * WAD - 1n) / assets + 1n : 0n;
+}

src/interest-rate-model/globalUtilization.ts

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+import WAD from "../fixed-point-math/WAD.js";
+
+export default function globalUtilization(assets: bigint, debt: bigint, backupBorrowed: bigint) {
+  return assets !== 0n && debt + backupBorrowed !== 0n ? ((debt + backupBorrowed) * WAD - 1n) / assets + 1n : 0n;
+}