Seed the RNG w/CSPRNG for higher quality cookies

[johnsonjh]

• Crypto-nerd pedantic change as cookie file is written with restrictive permissions, but standard Golang math/rand implementation is rather crap and any overhead from additional RNG seeding once per pktd start-up is so low enough to be essentially immeasurable across 150k runs.
• Edit: Verified (default) Golang runtime entropy retrieval on all our supported platforms is non-blocking, so no risk of causing any start-up time regressions in virtualized environments or when system entropy pool is near-exhausted.

[johnsonjh]

• Verified clean merge with recursive strategy against develop as of Thu Nov 26 02:01:32 PM EST 2020 + PR Improvement in bbolt/walletdb speed #111 + PR More reliably detect if we are current (or not.) #142 + PR Fix bug where pktctl -h would show help twice. #151 + PR blockchain: Avoid deadlock with additional locking #156 + PR peer: Default to 1s default trickle interval #160 + PR Optimization: Compare strings to a null string directly #168 + PR Fix cookie authentication; always show version information #175 + PR btcutil/hdkeychain/extendedkey.go: Fix a typo. #185 + PR Remove TTY detection #201 + PR peer/peer_test: Fix race conditions in peer test. #212 + PR README: Overhaul the text, include badges, links, etc. #220 + PR Update Travis to DPLv2: Move to Go 1.15.5, Focal & Catalina, Coveralls.io enabled, etc. #222 + PR Quiet some errors and warnings #223 + PR Add .revive.config.toml: Revive configuration file #224 + PR Use strictly compliant MD list item formatting #228 + PR Unmodularize GoLevelDB + use build tags for tests. #229 + PR Enable CodeQL analysis #230 + PR GoLevelDB: Various minor fixes and optimizations #231 + PR GoLevelDB: Remove unneeded comparison #232 + PR Add issue tracking bug reporting template. #233 + PR GoLevelDB: dbstress: time.Now().Sub -> time.Since #234 + PR GoLevelDB/dbstress: Fix trap of untrappable signal #235 + PR Fix some minor formatting, whitespace, tab issues #236 + PR Add PacketCrypt-2020-09-04.pdf to docs directory. #237 + PR Update StatsViz for custom frequency support #238

Auto-merging config.go
Merge made by the 'recursive' strategy.
 config.go | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

[johnsonjh]

Newly rebased PR #235 successfully verified against develop + #236 + #237 + #238 + #239 and base develop.

[johnsonjh]

• NOTE: Applied to WIP rebase branch successfully.