JKey has no equals() or hashCode() methods implemented

[artemananiev]

This issue was found during investigation of #7087.

OnDiskAccount has the following implementation of hashCode():

    @Override
    public int hashCode() {
        int result = Objects.hash(
                flags,
                key,
                memo,
                alias,
                hbarAllowances,
                fungibleAllowances,
                nftOperatorApprovals,
                firstStorageKeyNonZeroBytes);
        result = 31 * result + Arrays.hashCode(firstStorageKey);
        result = 31 * result + Arrays.hashCode(ints);
        result = 31 * result + Arrays.hashCode(longs);
        return result;
    }

One of the field above is key, which is of type JKey. This class has no hashCode() or equals() defined. Its hash code is different, even if two JKey objects are equal. Note that OnDiskAccount.equals() doesn't compare its key using its equals() method, but uses a different method instead:

                && equalUpToDecodability(this.key, that.key)

However, it doesn't make any sense. If this and that are actually equal, this equals() method may not be called as hashCode() may return different values. It makes OnDiskAccount unusable in Java collections, e.g. as a key in a map, or in a hash set, as well as all other similar classes with JKeys in their fields.

[jsync-swirlds]

equalUpToDecodability was recently added as part of the PBJ transition. It has some risks using for hashCode or equals, so it was left alone for the time being. I've now added both hashCode and equals, and a warning in the one point where things can go wrong (because Objects.toString() calls hashCode, which could produce an infinite recursion in rare conditions).