fix: build the mc status correctly

[zhiying-lin]

Description of your changes

copy latest imc status when the observedGeneration is matched with the imc generation.

After the fix,

1. MC gen : 2, IMC. gen 1, IMC condition gen 1
2. After copy, IMC gen 2 and send update IMC request to api server, IMC gen 2 in the memory
3. IMC gen != IMC condition
4. copy IMC status -> MC, stale info, do nothing
5. set MC condition gen 2 -> unknown
6. when imc collects the status gen 2 back, set MC condition gen 2 -> joined

Fixes #

I have:

• Run make reviewable to ensure this PR is ready for review.

How has this code been tested

unit tests + e2e tests

Special notes for your reviewer

[codecov]

Codecov Report

❌ Patch coverage is 96.77419% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../membercluster/v1beta1/membercluster_controller.go	96.77%	1 Missing ⚠️

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