fix(gloo): Update reconciler to detect change in gloo upstream spec

[sopida-chotwanwirach]

Problem:
The reconciler is not detecting changes in gloo upstream spec. When the slow start config is added or updated in gloo upstream, the same config is not propagated to existing flagger upstreams.

Reproducing Step:

• create gloo upstream

apiVersion: gloo.solo.io/v1
kind: Upstream
metadata:
  name: config-upstream
  namespace: gloo-system

• create canary that has upstream reference to gloo

apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: podinfo
  namespace: test
spec:
  upstreamRef:
    apiVersion: gloo.solo.io/v1
    kind: Upstream
    name: config-upstream
    namespace: gloo-system
  provider: gloo

• add/modify slow start config in gloo upstream

apiVersion: gloo.solo.io/v1
kind: Upstream
metadata:
  name: config-upstream
  namespace: gloo-system
spec:
  loadBalancerConfig:
    roundRobin:
      slowStartConfig:
        slowStartWindow: 2m
        minWeightPercent: 5

• flagger upstreams (primary and canary) will not pick up the updated slow start config

In PR:

• update reconciler to detect diff in load balancer config for gloo vs flagger upstreams
• when a change is detected, update flagger upstream load balancer with the latest config
• add integration test to verify the fix

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 30.43478% with 16 lines in your changes are missing coverage. Please review.

Project coverage is 56.51%. Comparing base (b778013) to head (e3a529e).
Report is 5 commits behind head on main.

Files	Patch %	Lines
pkg/router/gloo.go	30.43%	14 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1617      +/-   ##
==========================================
- Coverage   56.60%   56.51%   -0.09%     
==========================================
  Files          85       85              
  Lines        8549     8571      +22     
==========================================
+ Hits         4839     4844       +5     
- Misses       3038     3053      +15     
- Partials      672      674       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[stefanprodan]

LGTM

Thanks @sopida-chotwanwirach 🥇