Fix Field Access

[rcosta358]

Description

Fixes #238.
Fields are stored in the refinement context using this#name, but invocation targets were previously resolved using only name.

Example

private ByteBuffer buffer;

public Example() {
    buffer = ByteBuffer.wrap(new byte[128]);
    byte[] bytes = buffer.array();
}

Related Issue

#238.

Type of change

• Bug fix
• New feature
• Documentation update
• Code refactoring

Checklist

• Added/updated tests under liquidjava-example/src/main/java/testSuite/ (Correct* / Error*)
• mvn test passes locally
• Updated docs/README if behavior or API changed