fix: start xds server watchable map panics

[Xunzhuo]

Fixes: #734
Fixes: #747
Fixes: #838

Signed-off-by: bitliu bitliu@tencent.com

[codecov-commenter]

Codecov Report

Merging #745 (e550c4f) into main (6be6950) will decrease coverage by 0.51%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #745      +/-   ##
==========================================
- Coverage   63.62%   63.10%   -0.52%     
==========================================
  Files          47       47              
  Lines        5927     5979      +52     
==========================================
+ Hits         3771     3773       +2     
- Misses       1921     1971      +50     
  Partials      235      235              

Impacted Files	Coverage Δ
internal/infrastructure/kubernetes/service.go	48.33% <0.00%> (-27.00%)	⬇️
internal/provider/kubernetes/gateway.go	50.84% <0.00%> (-0.33%)	⬇️
internal/provider/kubernetes/httproute.go	58.53% <0.00%> (-0.73%)	⬇️
internal/provider/kubernetes/tlsroute.go	58.69% <0.00%> (-0.78%)	⬇️
internal/xds/server/runner/runner.go	23.65% <0.00%> (ø)
internal/provider/kubernetes/gatewayclass.go	75.36% <0.00%> (+1.44%)	⬆️

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[danehans]

I'd like to get #702 merged before merging this PR.

[danehans]

@Xunzhuo now that #702 has merged, can you rebase this PR and remove the draft?