Merge #988: installer: use -rpcauth for managed bitcoind

a997a7b gui: don't rely on cookie to check successful start (jp1ac4)
5e5c333 gui: use rpcauth in installer for internal bitcoind (jp1ac4)
7584b63 gui: start internal bitcoind with given config (jp1ac4)
b5980fb gui: add sections check to internal bitcoind config test (jp1ac4)
c3aad0f gui: add optional rpcauth to internal bitcoind config (jp1ac4)
e172ecd gui: move internal bitcoind config to bitcoind module (jp1ac4)

Pull request description:

  This is to resolve #929.

  The installer will generate an `rpcauth=` string for use in the managed bitcoind's bitcoin.conf file and will use the corresponding user and password in the Liana daemon config file.

  ~~The existence of the cookie file is still checked by `Bitcoind::start()` to determine if the process started successfully. An alternative approach could be considered in a follow-up PR (or as part of this one).~~

  For #924, we might still need to use the cookie path to stop an already-running process, as we would probably no longer have the password used to generate the previous `rpcauth=` string.

  Once #987 is merged, I'll update the Cargo files in this PR.

  In the first commit, I move some code from the installer to the bitcoind module. In the end, this wasn't strictly required for the other changes I made, but I kept it as I thought it made sense anyway.

ACKs for top commit:
  edouardparis:
    ACK a997a7b

Tree-SHA512: ec475bb3c82db4e30c42612e93c63e9b0387311a26d5433421f275e24ac5b0923eba9bd1daff612e60a6cf0bdcc10de0812ff69972237e6785c0835b5a31450f

Author: darosior

gui/Cargo.lock

@@ -42,6 +42,7 @@ toml = "0.5"
 chrono = "0.4"
 
 # Used for managing internal bitcoind
+base64 = "0.21"
 bitcoin_hashes = "0.12"
 reqwest = { version = "0.11", default-features=false, features = ["rustls-tls"] }
 rust-ini = "0.19.0"