Check validity rules on tip-sel and check-consistency only

[GalRogozinski]

Description

We want the rules added in #1786 to only be used when we are doing tip-selection and check consistency calls. This is so that IRI won't give an error when calculating the ledger state on old milestones that didn't adhere to the rule.

We have a boolean flag in the validate method that takes care of the 2 modes, that forces the extra checks.

Fixes #1746

Type of change

• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

Unit test have been added

• One unit test fails validation when the extra checks flag is set to true, on a bundle that will otherwise be valid.
• When the flag is set to false we verify that the extra checks are not being called

Checklist:

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

[GalRogozinski]

@acha-bill Taking a discussion from slack here about the behavior of GetBalances.

I think this doesn't hurt previously confirmed txs because the snapshot is being inspected directly here:

 for (final Hash address : addressList) {
                Long value = snapshotProvider.getLatestSnapshot().getBalance(address);
                if (value == null) {
                    value = 0L;
                }
                balances.put(address, value);
            }