Handling of empty CMake define

Nobody has claimed this yet.

### Brief Issue Summary

defines added to a project using `target_compile_definitions( PRIVATE EXAMPLE)` have the value `1` in the editor tooltip displays while the compiler sees them as no tokens / blank. This then causes parser errors because `1` isn't a valid token in a lot of places that macros are valid

### CMake Tools Diagnostics

```shell
{
"os": "win32",
"vscodeVersion": "1.79.2",
"cmtVersion": "1.14.33",
"configurations": [
{
"folder": "c:\\git\\test\\cmake-empty",
"cmakeVersion": "3.26.0",
"configured": true,
"generator": "Ninja",
"usesPresets": false,
"compilers": {
"C": "C:/Program Files/LLVM/bin/clang.exe",
"CXX": "C:/Program Files/LLVM/bin/clang++.exe"
}
}
],
"cpptoolsIntegration": {
"isReady": true,
"hasCodeModel": true,
"activeBuildType": "Debug",
"buildTypesSeen": [
"Debug"
],
"requests": [],
"responses": [],
"partialMatches": [],
"targetCount": 1,
"executablesCount": 1,
"librariesCount": 0,
"targets": [
{
"name": "hello_world",
"type": "EXECUTABLE"
}
]
},
"settings": [
{
"communicationMode": "automatic",
"useCMakePresets": "auto",
"configureOnOpen": true
}
]
}
```

### Debug Log

```shell
[main] Configuring project: cmake-empty
[proc] Executing command: "C:\Program Files\CMake\bin\cmake.EXE" --no-warn-unused-cli -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE -DCMAKE_BUILD_TYPE:STRING=Debug "-DCMAKE_C_COMPILER:FILEPATH=C:\Program Files\LLVM\bin\clang.exe" "-DCMAKE_CXX_COMPILER:FILEPATH=C:\Program Files\LLVM\bin\clang++.exe" -SC:/git/test/cmake-empty -Bc:/git/test/cmake-empty/build -G Ninja
[cmake] Not searching for unused variables given on the command line.
[cmake] -- Configuring done (0.0s)
[cmake] -- Generating done (0.0s)
[cmake] -- Build files have been written to: C:/git/test/cmake-empty/build
```

### Additional Information

[cmake-empty.zip](https://github.com/microsoft/vscode-cmake-tools/files/11844376/cmake-empty.zip)
Editor shows the define with the value `1` when the in code equivalent is `#define EXAMPLE` (i.e. nothing).
The compile_commands export shows the expected `-DEXAMPLE`

Blank defines added using `EXAMPLE=` (`-DEXAMPLE2=""` in compile_commands (unescaped)) do correctly show as blank but they happen to trigger a different bug in another editor the affected code is being used with so not a great workaround sadly

No source file or test is named. Reproduce the case using target_compile_definitions( PRIVATE EXAMPLE), then compare the editor tooltip with the compile_commands entry, which correctly shows -DEXAMPLE. Done means an empty CMake definition is displayed without the value 1 while preserving the existing handling of EXAMPLE=.

Written by the indexing model from the issue text.