Convert all values to pointers

[luksa]

This allows us to differentiate between unset values and values explicitly set to an empty value (e.g. "", 0, or false). Without this, users can't override the defaults set in e.g. profiles.

For example, cni.chained defaults to true. Previously, if a user set this value to false in the Istio resource, the operator would create the IstioRevision without this it, because it thought that the value wasn't set due to false being the zero value for booleans. The end result was that Istio CNI was deployed with chained set to true.

Now, all boolean, string, and int/float values are pointers. This allows the operator to know whether the user has set the value or not and, if set, carry the value to the IstioRevision resource.

[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 4 lines in your changes missing coverage. Please review.

Project coverage is 59.56%. Comparing base (62d9c90) to head (c028031).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...trollers/istiorevision/istiorevision_controller.go	75.00%	1 Missing and 1 partial ⚠️
pkg/istiovalues/overrides.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #433      +/-   ##
==========================================
+ Coverage   59.54%   59.56%   +0.02%     
==========================================
  Files          34       34              
  Lines        1656     1657       +1     
==========================================
+ Hits          986      987       +1     
  Misses        618      618              
  Partials       52       52              

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