Change CRASH_COND to ERR_FAIL in Cowdata::set

[qarmin]

Fixes #46395

Since #36311, some functions which used to ERR_FAIL macro inside PoolVector set function like

void Line2D::set_point_position(int i, Vector2 p_pos) {
	_points.set(i, p_pos);
	update();
}

now use Vector set function with CRASH_COND which cause a lot of crashes

Vector.h set function now

godot/core/vector.h

Line 83 in 63b0d82

_FORCE_INLINE_ void set(int p_index, const T &p_elem) { _cowdata.set(p_index, p_elem); }

and inside cowdata

godot/core/cowdata.h

Lines 136 to 141 in 6fc50d7

	_FORCE_INLINE_ void set(int p_index, const T &p_elem) {
	CRASH_BAD_INDEX(p_index, size());
	_copy_on_write();
	_get_data()[p_index] = p_elem;
	}

and PoolVector function

godot/core/pool_vector.h

Lines 490 to 497 in 6fc50d7

	template <class T>
	void PoolVector<T>::set(int p_index, const T &p_val) {
	ERR_FAIL_INDEX(p_index, size());
	Write w = write();
	w[p_index] = p_val;
	}

[akien-mga]

Some comments from IRC:

11:59 <@Akien> reduz: WDYT about #36476 ? Should we do that or change CowData to fail instead of crash?
12:03 <reduz> the GET functions should crash
12:03 <reduz> the set functions I don't know, I don't care either way

So maybe we can make CowData set ERR_FAIL instead of crashing.

[qarmin]

I think that is good to change in Cowdata::set CRASH_COND to ERR_FAIL to prevent crashes, but for more detailed errors a check like in Line2D from this PR should be provided.

[akien-mga]

Thanks!