Decomission api.testnet.solana.com

[mvines]

Problem

api.testnet.solana.com, api.beta.testnet.solana.com, api.edge.testnet.solana.com

These are underpowered GCP instances running https://github.com/solana-labs/solana-json-rpc-https-proxy because I was too lazy 6 months ago to setup TLS on the actual blockstreamer/RPC node. But this is now happening as a part of #4927, which obsoletes these three stooges.

Proposed Solution

Update:

• this repo,
• solana-web3.js,
• example-webwallet, maybe other examples
  to avoid the api.* URLs.

Then delete:

• api.testnet.solana.com
• api.beta.testnet.solana.com
• api.edge.testnet.solana.com