Add variable support for ctestArgs and ctestDefaultArgs

[Omotola]

Overview

Enables test-specific argument expansion in cmake.ctestArgs and cmake.ctestDefaultArgs using the ${testName}
placeholder. This allows users to generate per-test log files (e.g., --output-log /logs/${testName}.log) instead
of having all tests overwrite the same file.

Resolves #4416

Changes

• src/ctest.ts: Added ${testName} variable to the expansion options in getCTestArgs(). Added
  hasTestNameVariable() helper to detect usage.
• package.nls.json: Updated setting descriptions for ctestArgs and ctestDefaultArgs to document the new
  variable.

How it works

The ${testName} variable is expanded to the CTest test name when a single test is being executed:

Execution path	Behavior
Non-parallel mode	Expanded per-test in the sequential loop (each test gets its own ctest invocation)
Parallel mode, single test	Expanded when exactly one test is targeted
Parallel mode, multiple tests	Warning logged; variable left unexpanded (batch invocation has no single test
name)
Direct ctest path	Expanded when testsToRun contains exactly one entry

Example usage

// settings.json
{
    "cmake.ctestArgs": ["--output-log", "/logs/${testName}.log"]
}

Validation