improve finalising logic for canary release

[myname4423]

Ⅰ. Describe what this PR does

rewrite the doCanaryFinalising function, mainly to modify the logic of rollback
before, this function executes the same steps for rollback and other scenarios (including success, pause, disabling):

1. restore the stable service (remove selector)
2. finalizingBatchRelease
3. modify network configuration (ingress/istio/gateway api configuration), and route 100% traffic to stable pods
4. delete BatchRelease

however, in rollback scenario, running the first step (remove selector) will route some traffic unexpectedly to new version if user does A/B testing. Therefore, in rollback scenario, we instead route all traffic to stable service firstly, like:

1. route all traffic to stable service (by restoring ingress/istio/gateway api directly)
2. finalizingBatchRelease
3. delete BatchRelease
4. restore stable service, remove canary service

note: i am not intended to modify the behaviours other than rollback (ie. success, pause, disabling), however, i find it is possible to simplify it, by combing the first step and the third step:

1. call traffic finalising function to (restore stable service-> restore ingress/istio/gateway api -> remove canary service) in one go
2. finalizingBatchRelease
3. delete BatchRelease

Ⅱ. Does this pull request fix one issue?

no

Ⅲ. Special notes for reviews

[codecov]

Codecov Report

Attention: Patch coverage is 52.85714% with 33 lines in your changes missing coverage. Please review.

Project coverage is 44.76%. Comparing base (07c1731) to head (10f531d).
Report is 10 commits behind head on master.

Files	Patch %	Lines
pkg/controller/rollout/rollout_canary.go	54.54%	23 Missing and 7 partials ⚠️
pkg/controller/rollout/rollout_status.go	0.00%	2 Missing ⚠️
pkg/controller/rollout/rollout_progressing.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #229      +/-   ##
==========================================
+ Coverage   43.63%   44.76%   +1.12%     
==========================================
  Files          52       55       +3     
  Lines        5681     6103     +422     
==========================================
+ Hits         2479     2732     +253     
- Misses       2778     2910     +132     
- Partials      424      461      +37     

Flag	Coverage Δ
unittests	44.76% <52.85%> (+1.12%)	⬆️

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[furykerry]

/lgtm

[zmberg]

/lgtm
/approve

[kruise-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zmberg

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