[DO NOT MERGE] 1.6 release candidate tracking

[larskuhtz]

Pending Tasks:

• deploy release candidate bits (this branch) to Devnet
• Perform pending devnet tests
• full mainnet catchup of release candidate
• add kill switch to version 1.6, changelog  #921
• Populate CHANGELOG in version 1.6, changelog  #921

Pull Requests

Complete

• keep feature flag validation disabled #929 [keep feature flag validation disabled] (undoes effect of 919) (@larskuhtz)
  • code complete
  • merged
• Put pact v1.6 changes behind guard #926 [Put pact v1.6 changes behind guard] (@slpopejoy)
  • code complete
  • merged
• version 1.6, changelog  #921 [bump chainweb node version to 1.6] (@slpopejoy, @mightybyte)
  • code complete
  • approved
  • merged
• grandfather non-zero feature flags for block heights < 340000 #919 [grandfather non-zero feature flags for block heights < 340000]
  • merged
    The final constant should be around 75% into the respective DA epoch.
• Pact bump for execution config flags, enforce-one fix #916 [Pact bump for execution flags, enforce one fix] (@slpopejoy)
  • approved
  • merged
• Adds enriched message body to gas payer cap #912 [Adds enriched message body to gas payer caps] (@slpopejoy, @LindaOrtega)
  • approved
  • merged
• add --validate flag and output type none to header-dump #923, Fix github ci build on a full cache hit #928 [Fix GitHub CI builds for chainweb-node version changes] (@larskuhtz)
  • code complete
  • tested
  • merged

Testing:

Mainnet

• tests for grandfather non-zero feature flags for block heights < 340000 #919

  • complete catchup on mainnet01
  • mainnet01 catchup with tigger height of 200000 gets stuck at 199900 with The block has an invalid feature flag value

• tests for Disable feature flag validation. #920

  • complete catchup on mainnet01

• full mainnet01 catchup of final release candidate

Unit Tests

• Validation of mainet01 history:

  • verify that GitHub-ci job Validate mainnet01 history with build succeeds
  • verify that Gihub-ci job Validate mainet01 block header db succeeds

• Check that Gitbub-ci jobs are green for master and release/1.6 (except for the the Validate mainnet01 history with build, see above)

Devnet

• deploy release candidate (@larskuhtz)
• test guard for Adds enriched message body to gas payer cap #912 and Pact bump for execution config flags, enforce-one fix #916
• run full regression test suite (@ggobugi27)