doc: point release process at BGL tooling

[elianguitarra]

Summary:

• Point the release-process manpage step at the local devtools README instead of upstream bitcoin/bitcoin.
• Rename the config refresh step from bitcoin.conf/gen-bitcoin-conf.sh to BGL.conf/gen-BGL-conf.sh.

Validation:

• git diff --check
• rg -n gen-BGL-conf\.sh|gen-BGL-confsh|gen-manpagespy contrib\devtools\README.md doc\release-process.md

Bounty context:

• Submitted under the open Bitgesell PR bounty hunt: BGL PR bounty hunt ($10000 overall budget) #39
• Preferred payout if accepted/approved: USDT ERC20/BEP20 to 0xa3d7745af6E77ce825f0AF6DB94bA8073355E022