`strictRequired` should recognize properties defined in parent schema

**What version of Ajv are you using? Does the issue happen if you use the latest version?**

8.11.0

**Ajv options object**

```javascript
{ strict: true, strictRequired: true }
```

**JSON Schema**

```json
{
"type": "object",
"properties": {
"a": {"type": "number"},
"b": {"type": "number"},
"c": {"type": "number"},
"d": {"type": "number"}
},
"if": {
"required": ["a"]
},
"then": {
"required": ["b", "c"]
}
}
```

**Sample data**

(Does not compile)

**Your code**

```javascript
new Ajv({ strict: true }).compile({
type: "object",
properties: {
a: {type: "number"},
b: {type: "number"},
c: {type: "number"},
d: {type: "number"},
},
if: {
required: ["a"],
},
then: {
required: ["b", "c"],
},
})
```

**Validation result, data AFTER validation, error messages**

```
Error: strict mode: required property "a" is not defined at "#/if" (strictRequired)
```

**What results did you expect?**
No compile error

**Are you going to resolve the issue?**
I've tried digging into the error, but my attempts to solve it ended up making things worse... Will add notes in comments