While there are formatting description files for C/C++ (i.e., `.clang-format`), no equivalent formatting specification exists for CMake (to automatically format CMake files (e.g., `CMakeLists.txt`) consistently with `cmake-format`). This commit adds such a format description to ensure all CMake files are formatted consistently.

Most `get...()` functions have `has...()` equivalents (e.g., `getDefSVFGNode()` and `hasDefSVFGNode()`). However, certain getters (e.g., `getLLVMValue()`, `getLHSTopLevelPtr()` had no such existence-checking counterparts. This commit adds a number of these checking functions in cases where they were missing.

Note that these are for cases where the getters fail an assertion when no valid value exists. Cases where the getter simply returns a null-pointer on failure to find any corresponding values (e.g., `ICFG::getFunEntryBlock()`, `ICFG::getFunExitBlock()`, etc.), so a null-check can be used to catch cases where the getter fails to get any corresponding object, and thus don't need a corresponding existence checker. To avoid changing the current behaviour of the assertions and getters, I added additional existence-checking functions. This does mean the container will be searched twice (once in the existence-check and then again in the getter itself) and thus wastes performance. To avoid this, all current getters could be modified so that all getters return null-pointers on failures, but I didn't want to make such an intrusive change in this commit.

…istent with other WPA implementations)

Currently, most WPA implementations (e.g., `AndersenWaveDiff`) expose read-only functions (e.g., `printStat()`, `dumpTopLevelPtsTo()`, etc.) publically, as well as "constructors" like `solveAndWritePtsToFile()`, `readPtsFromFile()`, etc. However, `VersionedFlowSensitive` is the only one to mark these functions as `private`/`protected`. This makes it annoying to use polymorphism over the underlying PTA base class (i.e., `BVDataPTAImpl`) and the overridden virtual functions. This commit fixes that by marking these functions as public in the `VersionedFlowSensitive` WPA class.

This change allows me to use polymorphism to conveniently try different WPA backends like this:

```
SVF::BVDataPTAImpl *pta = nullptr;

switch(getChosenBackend()) {
    case Andersen_BASE:
        pta = new Andersen(...);
        break;
    case VFS_WPA:
        pta = new VersionedFlowSensitive(...);
        break;
    default:
        break;
}
```

…existing results

The current `SVFGBuilder` optimises the SVFG based on the command-line argument. However, when using SVF as a library, this is inconvenient. This commit changes the builder to use an additional flag to control optimisation behaviour.

Moreover, this commit fixes the reading/writing issues for optimised SVFGs. Currently, the writing happens post-optimisation, which causes the reading step to fail due to missing/unexpected nodes. This commit also ensures the *unoptimised SVFG* is written to a file *prior to optimising it*, and reads an unoptimised SVFG from a file and then optimises it. This fixes these crashing issues.

…ress errant warnings; added definitions of C++ aligned allocators (i.e., `new(align)`); defined all plain/no-throw/aligned/aligned-no-throw variants of C++ allocators for `size_t` defined as `unsigned int` and `unsigned long`; and defined `pvalloc()` and `strndup()` as allocators