feat: add support for hgctl gateway-config to retrieve higress gateway config

[Xunzhuo]

Ⅰ. Describe what this PR did

feat: add support for hgctl gateway-config to debug higress gateway xds config

1. support retrieve all configDump from specific higress gateway pod
2. support retrieve bootstrap config from specific higress gateway pod
3. support retrieve cluster config from specific higress gateway pod
4. support retrieve endpoint config from specific higress gateway pod
5. support retrieve listener config from specific higress gateway pod
6. support retrieve route config from specific higress gateway pod

xref: #229

examples:

[codecov-commenter]

Codecov Report

Merging #274 (8e00bc4) into main (affa120) will decrease coverage by 2.69%.
The diff coverage is 15.68%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #274      +/-   ##
==========================================
- Coverage   44.99%   42.30%   -2.69%     
==========================================
  Files          34       44      +10     
  Lines        5316     5779     +463     
==========================================
+ Hits         2392     2445      +53     
- Misses       2759     3163     +404     
- Partials      165      171       +6     

Impacted Files	Coverage Δ
pkg/cmd/hgctl/configBootstrap.go	0.00% <0.00%> (ø)
pkg/cmd/hgctl/configCluster.go	0.00% <0.00%> (ø)
pkg/cmd/hgctl/configCmd.go	0.00% <0.00%> (ø)
pkg/cmd/hgctl/configEndpoint.go	0.00% <0.00%> (ø)
pkg/cmd/hgctl/configListener.go	0.00% <0.00%> (ø)
pkg/cmd/hgctl/configRoute.go	0.00% <0.00%> (ø)
pkg/cmd/hgctl/root.go	0.00% <0.00%> (ø)
pkg/cmd/hgctl/configRetriever.go	23.75% <23.75%> (ø)
pkg/cmd/hgctl/utils.go	85.00% <85.00%> (ø)

... and 1 file with indirect coverage changes

[johnlanni]

cc @SpecialYang @gengleilei

[johnlanni]

LGTM