♻️ Add missing types on exported (#5203)

**Description**

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In order to toggle ON the flag `isolatedDeclarations` and allow us to
use something else than tsc to build our project (not sure we will do
one day), we start to make some types more explicit on our exported
symbols.

This PR does not fix everything as some of the fixes would require some
minor (subtle) breaking changes!

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- [x] My PR references one of several related issues (if any)
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- [x] My PR does not add any new dependency without an associated Issue
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- [x] My PR includes bumps details, please run `yarn bump` and flag the
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**Advanced**

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- [x] Category: ♻️ Refactoring
- [x] Impacts: None

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<!-- * ✨ Introduce new features -->
<!-- * 📝 Add or update documentation -->
<!-- * ✅ Add or update tests -->
<!-- * 🐛 Fix a bug -->
<!-- * 🏷️ Add or update types -->
<!-- * ⚡️ Improve performance -->
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generators in terms of generated values, if so which ones? when? -->
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.yarn/versions/4e927b19.yml

@@ -0,0 +1,8 @@
+releases:
+  fast-check: patch
+
+declined:
+  - "@fast-check/ava"
+  - "@fast-check/jest"
+  - "@fast-check/vitest"
+  - "@fast-check/worker"

packages/fast-check/src/check/symbols.ts

@@ -11,7 +11,7 @@
  * @remarks Since 1.8.0
  * @public
  */
-export const cloneMethod = Symbol.for('fast-check/cloneMethod');
+export const cloneMethod: unique symbol = Symbol.for('fast-check/cloneMethod');
 
 /**
  * Object instance that should be cloned from one generation/shrink to another

packages/fast-check/src/stream/Stream.ts

@@ -55,7 +55,7 @@ export class Stream<T> implements IterableIterator<T> {
   next(): IteratorResult<T> {
     return this.g.next();
   }
-  [safeSymbolIterator](): IterableIterator<T> {
+  [Symbol.iterator](): IterableIterator<T> {
     // /*DEBUG*/ this.closeCurrentStream();
     return this.g;
   }

packages/fast-check/src/utils/stringify.ts

@@ -28,7 +28,7 @@ const safePositiveInfinity = Number.POSITIVE_INFINITY;
  * @remarks Since 2.17.0
  * @public
  */
-export const toStringMethod = Symbol.for('fast-check/toStringMethod');
+export const toStringMethod: unique symbol = Symbol.for('fast-check/toStringMethod');
 /**
  * Interface to implement for {@link toStringMethod}
  *
@@ -62,7 +62,7 @@ export function hasToStringMethod<T>(instance: T): instance is T & WithToStringM
  * @remarks Since 2.17.0
  * @public
  */
-export const asyncToStringMethod = Symbol.for('fast-check/asyncToStringMethod');
+export const asyncToStringMethod: unique symbol = Symbol.for('fast-check/asyncToStringMethod');
 /**
  * Interface to implement for {@link asyncToStringMethod}
  *