feat: templatize values

[vbehar]

instead of using raw values - such as {{ .Values.some.thing }} - let's wrap them with the tpl function.

the previous example would then be rendered as {{ tpl (.Values.some.thing) $ }}

So that we can reference other values from inside our values for example.

[arttor]

Hi @vbehar! Thank you for your contribution. The proposal looks very interesting but i see several potential problems:

• the change is quite big and it is better to hide it under a feature flag to not surprise users after upgrading to a new version
• overusing tpl function may lead to performance issues see
• in the PR, not all template values are wrapped into tpl. How to decide which one should be wrapped?