wallet+chain: add new APIs GetPeerInfo, GetBlockChainInfo, and RawRequest to chain interface

[mohamedawnallah]

Description

In this commit, we add new APIs to chain interface used across btcd, neutrino, and bitcoind chain backends. The new APIs are GetPeerInfo, GetBlockChainInfo, and RawRequest.

Addresses part of lightningnetwork/lnd#7951.
Dependent PR lightningnetwork/lnd#9435.

Motivation and Context

The motivation behind adding those APIs is to easier the process of unifying RPC connection creations across chain backends as part of LND Daemon.

[Roasbeef]

Approved CI.

[mohamedawnallah]

It looks like approval is required whenever an updated commit is submitted. Additionally, it doesn’t seem to be configured to trigger against the master branch in the forked repository.

I'm also unsure about the linting process when running make lint locally. For example, I'm encountering linting issues for code blocks I haven’t modified, such as FilterBlocks and handler:

chain/btcd.go:316: Function 'FilterBlocks' is too long (77 > 60) (funlen)
func (c *BtcdClient) FilterBlocks(
chain/btcd.go:496: Function 'handler' is too long (72 > 60) (funlen)
func (c *BtcdClient) handler() {
rpc/legacyrpc/methods.go:974: Function 'help' is too long (78 > 60) (funlen)
func help(icmd interface{}, _ *wallet.Wallet,
rpc/legacyrpc/methods.go:1593: Function 'signRawTransaction' has too many statements (86 > 40) (funlen)
...

EDIT:
How am I supposed to move this PR forward? The linter is requiring considerable code refactoring of the FilterBlocks, handler, and help functions after modifying their signatures. However, these refactoring changes are unrelated to the PR's original purpose. What's the best way to handle this situation?

[Roasbeef]

How am I supposed to move this PR forward? The linter is requiring considerable code refactoring of the FilterBlocks, handler, and help functions after modifying their signatures. However, these refactoring changes are unrelated to the PR's original purpose. What's the best way to handle this situation?

Usually in other projects we're able to specifying a starting commit in the linter. It only attempts to flag linting errors of new changes after that commit. Looks like we're missing that config here.

So I think we should either add that starting commit (here's an example for lnd), or we can move forward wit hthis PR, verifying that no new linter violations are hit.

[Abdulkbk]

Thanks for the PR @mohamedawnallah. Before diving into the changes, I have a quick question: would renaming RPCClient to BtcdClient here result in backward compatibility issues for projects using btcwallet, or are we assuming that only LND uses it?

[yyforyongyu]

Thanks for the PR @mohamedawnallah. Before diving into the changes, I have a quick question: would renaming RPCClient to BtcdClient here result in backward compatibility issues for projects using btcwallet, or are we assuming that only LND uses it?

Good question. I think we should keep it backward compatible. Maybe keep RPCClient and point it to BtcdClient? Many other projects use this package.