[Docs] Update docs that refer to libraries from azure-sdk-for-node to refer to those in azure-sdk-for-js

[ramya-rao-a]

• Content in some handwritten docs such as Azure modules for JavaScript and Get started with the Azure modules for Node.js are no longer maintained. Consider retiring them
• All existing conceptual docs need to be updated to use the "@azure/arm-" packages instead of "azure-arm" packages
• The reference docs for the new packages should move to the respective service nodes instead of living under "Others". For example: https://docs.microsoft.com/en-us/javascript/api/@azure/arm-appservice/?view=azure-node-latest
• The reference docs for older packages should be marked as deprecated
• Consider redirecting users from the package summary page to the Javascript API browser

Related to #4291

[ramya-rao-a]

cc @kaerm

[kaerm]

1. We can work out to put our own content there - probably worth working across various languages. @kaerm will create a scaffolding and get back to @ramya-rao-a to help get it filled
2. To be done together with samples
3. Will confirm soon that we need to work on it. If so, we should either change this document to account for the right service placement in the tree or submit a work item to the docs team (aka.ms/publish-on-docs).
4. Two ways of doing that.
   Option 1. We can do that by following the instructions for all packages (or requesting the docs to do it)
   Option 2. We can edit the tree linked in 3 to add a Legacy category (non ideal but faster).
5. Ongoing effort, currently analyzing developer flow, will be changed across languages later

[ramya-rao-a]

Closing as all the points have now been addressed