Rename master key to seed

Summary:
131d4450b scripted-diff: Rename master key to seed (John Newbery)
This only includes non-behavioral changes.

Commit Description:

-BEGIN VERIFY SCRIPT-

ren() { git grep -l "\<$1\>" 'src/*.cpp' 'src/*.h' test | xargs sed -i "s:\<$1\>:$2:g"; }
ren GenerateNewHDMasterKey  GenerateNewSeed
ren DeriveNewMasterHDKey    DeriveNewSeed
ren SetHDMasterKey          SetHDSeed
ren hdMasterKeyID           hd_seed_id
ren masterKeyID             seed_id
ren SetMaster               SetSeed
ren hdmaster                hdseed

-END VERIFY SCRIPT-

Partial backport of Core PR12924
https://github.com/bitcoin/bitcoin/pull/12924/commits/131d4450b913fa4f00dc8b176dc996d39f786c19

Depends on D4207

Test Plan:

make check
test_runner.py

grep for the above master(key) variations. Only inactivemasterkey should show up in rpcdump.cpp and wallet_dump.py, and hdmasterkey in rpcdump.cpp and wallet_dump.py.

Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: deadalnix, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D4190