Update CDN domain for Functions VS Code extension

[mattchenderson]

We need to change from functionscdn.azureedge.net to cdn.functions.azure.com and from functionscdnstaging.azureedge.net to cdn-staging.functions.azure.com.

In this repo, there is a direct dependency in the fallback logic:

vscode-azurefunctions/src/utils/bundleFeedUtils.ts

Line 119 in 6b74122

const baseUrl: string = envVarUri || `https://functionscdn${suffix}.azureedge.net/public`;

Note that this would need to change how we apply the suffix, as well.

The old domain is also indirectly referenced through a few aka links:

vscode-azurefunctions/src/utils/bundleFeedUtils.ts

Line 116 in 6b74122

url = 'https://aka.ms/AA66i2x';

vscode-azurefunctions/src/utils/cliFeedUtils.ts

Line 14 in bd6d276

const funcCliFeedV4Url: string = 'https://aka.ms/AAbbk68';

vscode-azurefunctions/src/utils/bundleFeedUtils.ts

Line 54 in bd6d276

const versionArray: string[] = await feedUtils.getJsonFeed(context, 'https://aka.ms/azFuncBundleVersions');

This repo also makes reference to it both directly and through aka links in this readme:

vscode-azurefunctions/src/templates/README.md

Line 3 in bd6d276

The code in this folder is used to parse and model the [function templates](https://github.com/Azure/azure-webjobs-sdk-templates) provided by the [Azure Functions CLI Feed](https://aka.ms/AAbbk68). The Functions CLI Feed provides a central location to get the latest version of all templates used for functions.

vscode-azurefunctions/src/templates/README.md

Line 27 in bd6d276

Basic script templates (i.e. http and timer) are retrieved from the 'templates' property in each entry of the [CLI Feed](https://aka.ms/AAbbk68). More advanced templates (i.e. blob and cosmos) are retrieved from another feed specific to the extension bundle for that project. For example, the default bundle is 'Microsoft.Azure.Functions.ExtensionBundle' and the matching feed is https://functionscdn.azureedge.net/public/ExtensionBundles/Microsoft.Azure.Functions.ExtensionBundle/index-v2.json

[mattchenderson]

See Azure/Azure-Functions#2576 for other related issues across other Functions repos