Consolidate subtensor installation docs

[rajkaramchedu]

The local subtensor node installation docs are now in multiple places (1 and 2 below). Consolidate them so we have only a single source of truth.

1. This: https://github.com/opentensor/subtensor/blob/development/docs/running-subtensor-locally.md (remove this and add a link to the below (2) on the docs site page).
2. https://docs.bittensor.com/subtensor-nodes/using-source
3. Fix the bootnode in this script by making it the same as the ones used in the the above (2): https://github.com/opentensor/subtensor/blob/development/scripts/run/subtensor.sh
4. Note that the above "subtensor.sh" is documented for only Docker method.
5. Merge the development branch README in subtensor repo into its main branch.
6. Add the step to switch to "main" branch for the subtensor repo in this doc and other docs in this directory: https://github.com/opentensor/bittensor-subnet-template/blob/main/docs/running_on_staging.md A user could not mint test tokens from faucet from the default "development" branch. See Discord thread: https://discord.com/channels/799672011265015819/1235626064886108160
   cc: @sam0x17