Don't use a mutex for computing Reference hash

[pepone]

I don't think we should use any mutex in this code.

Either the hash is very cheap to compute and we compute it each time. Or it's somewhat expensive to compute (== bad hash) and we compute it in the constructor. As far as I can tell, this class is immutable.

Originally posted by @bernardnormier in https://github.com/zeroc-ice/ice/pull/1707#pullrequestreview-1836571809

[bernardnormier]

Fixed by #2120 in C#. Fixed by #2123 in C++.

[InsertCreativityHere]

Fixed by #2437 in Java. And Javascript has no mutex locking.

[bernardnormier]

ice % rg hashInit
js/src/Ice/Reference.js
45:        this._hashInitialized = false;
265:        if (this._hashInitialized) {
285:        this._hashInitialized = true;
990:        if (!this._hashInitialized) {

js/src/Ice/IPEndpointI.js
77:            this._hashCode = this.hashInit(5381);
170:    hashInit(h) {

js/src/Ice/TcpEndpointI.js
185:    hashInit(h) {
186:        h = super.hashInit(h);

Unfortunately, while JS doesn't use a mutex, it uses the undesirable "hash value caching" logic. Still needs to be fixed.

[pepone]

JavaScript fixed in #2607