refactor(core-node): Remove StateAccumulatorV1and rename StateAccumulatorV2

[bingyanglin]

Description of change

• Remove StateAccumulatorV1
  • remove notify_read_checkpoint_state_digests (only used in StateAccumulatorV1)
• Remove the following always true logic
  • state_accumulator_v2_enabled
  • state_accumulator_v2 because it is now always true
  • with_state_accumulator_v2_enabled
• Rename with_state_accumulator_v2_enabled_config to be with_state_accumulator_config
  • Note that now state_accumulator_v2 is always enabled and can be configured
• Rename state_accumulator_v2_enabled_config to be state_accumulator_config
• Rename validator_state_accumulator_v2_enabled_config to be validator_state_accumulator_config
• Set the default state_accumulator_config to be Global(true)
• Rename with_state_accumulator_v2_enabled_callback to be with_state_accumulator_callback

Links to any relevant issues

Closes #3259

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How the change has been tested

• I was running the local network with RUST_LOG=info cargo run --release --bin iota start --force-regenesis --with-faucet

Change checklist

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked that new and existing unit tests pass locally with my changes

[alexsporn]

Remove these flags and make it default behaviour.

[bingyanglin]

Thanks. Those flags are removed in 494bcfd.
Also it was mad default behaviour like here, with commits 78fe7e6 and 3a1fde3.