Symbols generated by Devito should be generated using a symbol registry

[EdCaunt]

Symbols generated within Devito currently do not have guaranteed unique names, potentially producing inadvertent clashes which result in cryptic errors being raised.

Devito currently makes use of counters (among other means) to create unique names for internally-generated symbols. However, there is nothing preventing clashes either with other generated symbols or those defined by the user.

It would be beneficial to have a registry of symbols to generate unique names in a consistent manner, to be used throughout the codebase.

This functionality could potentially be introduced as a mixin class where needed.

Possible approach:

@cached_property
def name(self):
    if self._name is None:
         return compute_deterministic_hash(self._hashable_content()))
    else:
         return self._name 

or alternatively when setting name:

self._name = self._registry.get_unique_name(name)

where get_unique_name adds an increment to the supplied name as required.