Add Istio egress CLI commands

[nshankar13]

---

This PR adds the CLI commands to az aks mesh for enable-egress-gateway and disable-egress-gateway. It also vendors the python Kubernetes client under src/aks-preview/azext_aks_preview/vendored_sdks/kubernetes. The Kubernetes client is used to create a StaticGatewayConfiguration custom resource prior to enabling the egress gateway for the live tests, as this is required on the RP side to enable an Istio egress gateway.

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Related command

az aks mesh enable egress gateway

General Guidelines

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[azure-client-tools-bot-prd]

⚠️Azure CLI Extensions Breaking Change Test

⚠️aks-preview

rule	cmd_name	rule_message	suggest_message
⚠️ 1001 - CmdAdd	aks mesh disable-egress-gateway	cmd aks mesh disable-egress-gateway added
⚠️ 1001 - CmdAdd	aks mesh enable-egress-gateway	cmd aks mesh enable-egress-gateway added

[azure-client-tools-bot-prd]

Hi @nshankar13,
Since the current milestone time is less than 7 days, this pr will be reviewed in the next milestone.

[yonzhan]

Thank you for your contribution! We will review the pull request and get back to you soon.

[github-actions]

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Please sync the latest code with latest dev branch (for azure-cli) or main branch (for azure-cli-extensions).
After that please run the following commands to enable git hooks:

pip install azdev --upgrade
azdev setup -c <your azure-cli repo path> -r <your azure-cli-extensions repo path>

[github-actions]

• For more info about extension versioning, please refer to Extension version schema

[FumingZhang]

the change generally looks good to me, please fix failed checks

/mnt/vss/_work/1/s/src/aks-preview/azext_aks_preview/_params.py:2228:1: W293 blank line contains whitespace
/mnt/vss/_work/1/s/src/aks-preview/azext_aks_preview/_validators.py:857:1: E302 expected 2 blank lines, found 1
/mnt/vss/_work/1/s/src/aks-preview/azext_aks_preview/_validators.py:861:5: F841 local variable 'asm_egress_name_regex' is assigned to but never used
/mnt/vss/_work/1/s/src/aks-preview/azext_aks_preview/_validators.py:862:13: F821 undefined name 'asm_revision_regex'
/mnt/vss/_work/1/s/src/aks-preview/azext_aks_preview/_validators.py:864:56: F821 undefined name 'revision'
/mnt/vss/_work/1/s/src/aks-preview/azext_aks_preview/_validators.py:866:1: E302 expected 2 blank lines, found 1
/mnt/vss/_work/1/s/src/aks-preview/azext_aks_preview/custom.py:3144:1: E302 expected 2 blank lines, found 1
/mnt/vss/_work/1/s/src/aks-preview/azext_aks_preview/managed_cluster_decorator.py:2413:1: W293 blank line contains whitespace

• FAIL - HIGH severity: missing_parameter_help
  Parameter: aks mesh disable-egress-gateway, egress_gateway_name - Missing help
  Parameter: aks mesh disable-egress-gateway, egress_gateway_namespace - Missing help
  Parameter: aks mesh enable-egress-gateway, egress_gateway_name - Missing help
  Parameter: aks mesh enable-egress-gateway, egress_gateway_namespace - Missing help

bypass in src/aks-preview/linter_exclusions.yml

• FAIL - HIGH severity: option_length_too_long
  Parameter: aks mesh disable-egress-gateway, egress_gateway_namespace - The lengths of all options ['--egress-gateway-namespace'] are longer than threshold 22. Argument egress_gateway_namespace must have a short abbreviation.
  Parameter: aks mesh enable-egress-gateway, egress_gateway_namespace - The lengths of all options ['--egress-gateway-namespace'] are longer than threshold 22. Argument egress_gateway_namespace must have a short abbreviation.
  Parameter: aks mesh enable-egress-gateway, gateway_configuration_name - The lengths of all options ['--gateway-configuration-name'] are longer than threshold 22. Argument gateway_configuration_name must have a short abbreviation.