[3.x] Initialize all variables in constructor to prevent undefined behavior

[qarmin]

Issue description

3.x version of #43636

Due using unitialized variables, Godot may behave very strange and cause bugs like #52634.
To prevent such situations, all variables(except maybe buffers) should be initialized in constructor, because it is easy to forget to do it later.

So, initializing all variables in such class

class HashingContext : public Reference {
	void *ctx;
        int rar;
        bool q;
public:
	HashingContext() {
            ctx = memnew(something);
        }
	~HashingContext();
};

can be done in this way in 3.x branch

class HashingContext : public Reference {
	void *ctx;
        int rar;
        bool q;
public:
	HashingContext() {
            ctx = memnew(something);
            rar = 0;
            q = false;
        }
	~HashingContext();
};

Do not try to create PR which changes more than ~50-100 lines, because it will be hard to rebase after other users changes and also such small PR should be merged faster into 3.x branch.

Maybe cppcheck html report will be helpful to find such variables - report.zip

Remember to put here info that you work on e.g. core/ or servers/ folder

[greeshmaym]

Hey @qarmin, Can you assign this issue to me.I would like to work on this

[qarmin]

You need just write in what folder you are working in and no one else should bother you.
Remember to create a PR of max 50-100 lines and if you want to change more things, it is best to create another PR.

[Kyetuur]

I'm going to look at /scene

[qarmin]

PR for this issue should be created against 3.x branch, not master(don't close PR, master branch is handled via this issue - #43636 ).

[HuanLe02]

Hello. I will take a look at /servers.

[lukan23]

Hello, I'm going to look at /platform

[splitsecmsk]

Hello, I'm going to look at /drivers

[Lucas3H]

Hi guys, I'll work on /editor folder.

[bjauny]

I'll take a look at /core!