[Bug] PrivateIdentifier nodes are omitted from 2020 semantic classifications

# Bug Report

### 🔎 Search Terms

semantic highlighting, semantic token, PrivateIdentifier, private field, private method, encodedSemanticClassifications

### 🕗 Version & Regression Information

- TypeScript 6.0.3 (bundled with VS Code)
- Also present in the v5.9 classifier implementation
- This is not a theme-specific issue

### 💻 Code

```ts
class Foo {
field = 1;
#privateField = 1;

method() {}
#privateMethod() {}

test() {
this.field;
this.#privateField;

this.method();
this.#privateMethod();
}
}
```

### 🙁 Actual behavior

In VS Code's **Developer: Inspect Editor Tokens and Scopes**:

- `field` and `method` receive semantic token types.
- `#privateField` and `#privateMethod` receive no semantic token and fall back to TextMate scopes.
- As a result, `editor.semanticTokenColorCustomizations` rules for `property` and `method` do not apply to ECMAScript private members.

### 🙂 Expected behavior

- `#privateField` should be classified as `property`.
- `#privateMethod` should be classified as `method`.
- Declarations should also receive the `declaration` modifier.

### Root cause

VS Code requests `encodedSemanticClassifications-full` with format `"2020"`.

In `src/services/classifier2020.ts`, `collectTokens` only enters the semantic-classification path for `isIdentifier(node)`:

```ts
if (isIdentifier(node) && ...) {
let symbol = typeChecker.getSymbolAtLocation(node);
// ...
}
```

ECMAScript private names are separate `SyntaxKind.PrivateIdentifier` nodes, so they are skipped before `getSymbolAtLocation` is called.

Relevant source:
https://github.com/microsoft/TypeScript/blob/050880ce59e30b356b686bd3144efe24f875ebc8/src/services/classifier2020.ts#L121-L203

### Proposed fix

```diff
+ isPrivateIdentifier,
isPropertyAccessExpression,
```

```diff
- if (isIdentifier(node) && ...) {
+ if ((isIdentifier(node) || isPrivateIdentifier(node)) && ...) {
```

The existing declaration-kind mapping already classifies private fields and methods correctly once these nodes reach the symbol-classification path.

I tested the equivalent change against TypeScript 6.0.3:

- `#privateField` declaration/reference → `property`
- `#privateMethod` declaration/reference → `member` internally, mapped by VS Code to `method`
- declaration occurrences receive the `declaration` modifier
- added fourslash regression test passes

### Related issue

https://github.com/microsoft/TypeScript/issues/44483 requests new `private`/`protected` semantic modifiers. This report is different: ECMAScript `PrivateIdentifier` nodes currently receive no semantic classification at all.

Commencez dans src/services/classifier2020.ts, au niveau de collectTokens, et examinez le mappage existant de declaration-kind pour les nœuds identificateurs. Ajoutez le test de régression fourslash pertinent couvrant les déclarations et les références de champs et de méthodes private, puis vérifiez que les nœuds reçoivent les classifications property ou method et les declaration modifiers.

Rédigé par le modèle d'indexation à partir du texte de l'issue.