add Cached::cache_try_get_or_set_with

[wbenny]

This commit adds a new trait method Cached::cache_try_get_or_set_with and implements it for all cache variants in the code.

This method was already available for async, but there was no way how to do the same in the sync code.

Each module follows slightly different coding styles, so I tried to match a coding style for each particular module.

Tests were extended for every implementation (mostly inspired by their already existing async counterparts).

[wbenny]

Hi, can I do something to help push this though? I would really love to ditch my fork from Cargo.toml :)

[jaemk]

Sorry I've been absent @wbenny. Assuming the tests pass, PR looks good and I can push a new version