fix: apply ssa namespace twice

[blakepettersson]

In argoproj/argo-cd#13965, upgrading to client-go 0.26 uncovered an issue with existing namespaces not preserving labels and annotations when converting an existing namespace to use managedNamespaceMetadata.

From 0.26 up, in order to preserve the existing behaviour what we need to do is to first apply the existing namespace with SSA and its preexisting labels and annotations. This also needs to be applied with another manager than the default one.

After that initial apply, we proceed as normal with a ServerSideApply. This is a one-time thing for any existing namespace; we check if we need to perform this action by detecting if there is a preexisting SSA annotation on the namespace.

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Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (f15cf61) 54.63% compared to head (0115c94) 54.64%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #537   +/-   ##
=======================================
  Coverage   54.63%   54.64%           
=======================================
  Files          41       41           
  Lines        4638     4652   +14     
=======================================
+ Hits         2534     2542    +8     
- Misses       1908     1912    +4     
- Partials      196      198    +2     

Files	Coverage Δ
pkg/sync/sync_context.go	73.81% <62.50%> (-0.27%)	:arrow_down:

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Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

No Coverage information
0.0% Duplication