Cherry pick AppGw changes into master

[anton-evseev]

Cherry pick #4996 into master

Contribution checklist:

• I have reviewed the documentation for the workflow.
• Validation tools were run on swagger spec(s) and have all been fixed in this PR.
• The OpenAPI Hub was used for checking validation status and next steps.

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[openapi-portal-comment]

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[AutorestCI]

Automation for azure-sdk-for-ruby

Nothing to generate for azure-sdk-for-ruby

[AutorestCI]

Automation for azure-sdk-for-python

The initial PR has been merged into your service PR:
Azure/azure-sdk-for-python#4193

[AutorestCI]

Automation for azure-sdk-for-go

The initial PR has been merged into your service PR:
Azure/azure-sdk-for-go#3925

[azuresdkci]

Can one of the admins verify this patch?

[anton-evseev]

Once again CI fails with out of memory exception

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory\n 1: node::Abort() [node]\n 2: 0x8ccf9c [node]\n 3: v8::Utils::ReportOOMFailure(char const*, bool) [node]\n 4: v8::internal::V8::FatalProcessOutOfMemory(char const*, bool) [node]\n 5: v8::internal::Factory::NewFixedArray(int, v8::internal::PretenureFlag) [node]\n 6: v8::internal::HashTable<v8::internal::StringTable, v8::internal::StringTableShape>::NewInternal(v8::internal::Isolate*, int, v8::internal::PretenureFlag) [node]\n 7: v8::internal::HashTable<v8::internal::StringTable, v8::internal::StringTableShape>::New(v8::internal::Isolate*, int, v8::internal::PretenureFlag, v8::internal::MinimumCapacity) [node]\n 8: v8::internal::HashTable<v8::internal::StringTable, v8::internal::StringTableShape>::EnsureCapacity(v8::internal::Handle<v8::internal::StringTable>, int, v8::internal::PretenureFlag) [node]\n 9: v8::internal::StringTable::LookupString(v8::internal::Isolate*, v8::internal::Handle<v8::internal::String>) [node]\n10: v8::internal::RegExpResultsCache::Enter(v8::internal::Isolate*, v8::internal::Handle<v8::internal::String>, v8::internal::Handle<v8::internal::Object>, v8::internal::Handle<v8::internal::FixedArray>, v8::internal::Handle<v8::internal::FixedArray>, v8::internal::RegExpResultsCache::ResultsCacheType) [node]\n11: v8::internal::Runtime_StringSplit(int, v8::internal::Object**, v8::internal::Isolate*) [node]\n12: 0x221ef3a042fd\nAborted (core dumped)]'

[AutorestCI]

Automation for azure-sdk-for-js

A PR has been created for you based on this PR content.

Once this PR will be merged, content will be added to your service PR:
Azure/azure-sdk-for-js#937

[AutorestCI]

Automation for azure-sdk-for-node

The initial PR has been merged into your service PR:
Azure/azure-sdk-for-node#4555

[AutorestCI]

Automation for azure-sdk-for-java

Nothing to generate for azure-sdk-for-java

[anton-evseev]

@jianghaolu please take a look