The 0.35 release cycle renamed the 'fastsync' functionality to 'blocksync'. This change brings the configuration parameters in line with that change. Namely, it updates the configuration file `[fastsync]` field to be `[blocksync]` and changes the command line flag and config file parameters `--fast-sync` and `fast-sync` to `--enable-block-sync` and `enable-block-sync` respectively.

Error messages were added to help users encountering these changes be able to quickly make the needed update to their files/scripts.

When using the old command line argument for fast-sync, the following is printed

```
./build/tendermint start --proxy-app=kvstore --consensus.create-empty-blocks=false --fast-sync=false
ERROR: invalid argument "false" for "--fast-sync" flag: --fast-sync has been deprecated, please use --enable-block-sync
```

When using one of the old config file parameters, the following is printed:
```
./build/tendermint start --proxy-app=kvstore --consensus.create-empty-blocks=false
ERROR: error in config file: a configuration parameter named 'fast-sync' was found in the configuration file. The 'fast-sync' parameter has been renamed to 'enable-block-sync', please update the 'fast-sync' field in your configuration file to 'enable-block-sync'
```

This is just a configuration change to default to using the new stack
unless explicitly disabled (e.g. `UseLegacy`) this renames the
configuration value and makes the configuration logic more clear.

The legacy option is good to retain as a fallback if the new stack has
issues operationally, but we should make sure that most of the time
we're using the new stack.

EDIT: Updated, see [comment below]( https://github.com/tendermint/tendermint/pull/6785#issuecomment-897793175)

This change adds a sketch of the `Debug` mode. 

This change adds a `Debug` struct to the node package. This `Debug` struct is intended to be created and started by a command in the `cmd` directory. The `Debug` struct runs the RPC server on the data directories: both the state store and the block store.

This change required a good deal of refactoring. Namely, a new `rpc.go` file was added to the `node` package. This file encapsulates functions for starting RPC servers used by nodes. A potential additional change is to further factor this code into shared code _in_ the `rpc` package. 

Minor API tweaks were also made that seemed appropriate such as the mechanism for fetching routes from the `rpc/core` package.

Additional work is required to register the `Debug` service as a command in the `cmd` directory but I am looking for feedback on if this direction seems appropriate before diving much further.

closes: #5908

* node: minimize hardcoded service initialization

* hacking

* nil safety

* reduce space

* remove genesis state store

* fix lint

* fix pex

* unwind some odering effects

* fix tests

* remove unused experiment

closes #2498 
solves part of #3365

Note: difficult to test the event emit in SwitchToFastSync part, might need to change `stateSyncReactor` to an interface in the `nodeImpl` struct

## Description

Expose p2p functions for use in the sdk. 

These functions could also be copied over to the sdk. I dont have a preference of which is better.

use  `maxPeerBlockHeight` information to show the current network's best height.

Closes #3983
Relate to #3365

ref: the`highestBlock` in the response of `eth.isSyncing` call
https://web3js.readthedocs.io/en/v1.3.4/web3-eth.html#issyncing

Closes #3507

This PR make some tweaks to backfill after running e2e tests:
- Separates sync and backfill as two distinct processes that the node calls. The reason is because if sync fails then the node should fail but if backfill fails it is still possible to proceed.
- Removes peers who don't have the block at a height from the local peer list. As the process goes backwards if a node doesn't have a block at a height they're likely pruning blocks and thus they won't have any prior ones either. 
- Sleep when we've run out of peers, then try again.

state: move pruneBlocks function from consensus/state to state/execution

Closes #5414

Addresses a beginning component of #6255

Pass a set of private peer ids to the `PeerManager` and any node that exists in this set is not returned in the `Advertise` method.

closes: #6405