fix: default LB AllocatedOutboundPorts to 0

[jackfrancis]

Reason for Change:

This PR sets the AllocatedOutboundPorts configuration to 0, as this is a preferred default configuration for LB outbound rules.

0 is equivalent to "automatic", which means is preferable to the Azure-provided default of 1024 , which essentially caps SNAT ports at that number.

See here for more info:

https://docs.microsoft.com/en-us/azure/load-balancer/load-balancer-outbound-rules-overview

Issue Fixed:

Fixes #2558

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[codecov]

Codecov Report

Merging #2526 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2526      +/-   ##
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+ Coverage   71.79%   71.79%   +<.01%     
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  Files         131      131              
  Lines       24787    24789       +2     
==========================================
+ Hits        17795    17797       +2     
  Misses       5966     5966              
  Partials     1026     1026

[Michael-Sinz]

Setting this to 4096 is not a good default as it will keep clusters to under 15 nodes.

Setting this to 0 will use the adaptive behavior of the LB:

https://docs.microsoft.com/en-us/azure/load-balancer/load-balancer-outbound-rules-overview#snatports

The option/value to set a fixed smaller number (say 32, in order to be able to reach 1000 nodes like the automatic table says) to prevent the strange networking problem when crossing a VM count boundary as describe here:

https://docs.microsoft.com/en-us/azure/load-balancer/load-balancer-outbound-connections#preallocatedports

[jackfrancis]

We will do #2377 as a follow-up PR to make this configurable

[Michael-Sinz]

Looks good to me and matches how I have manually tested the creation of clusters for our systems.

This extra value (set to 0) matches how prior Azure load balancer setup was done in the past and allows scaling into the hundreds of VMs in our clusters.

At some point it would be nice to allow specifying a specific value here but it is a complex set of choices for people and the automatic setting provides the best tradeoff for the general rule.

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