Enhancements to YBD payload after assessment refactoring

[sanyamsinghal]

Describe the changes in this pull request

• Need to add Migration Complexity Explainability to YBD and bump up the payload version
• Ensure assessment issue struct in ybd and assessment are in sync
• Bump up the payload version

Describe if there are any user-facing changes

Yes but it is backward compatible.
Also the payload would change for YugabyteD, wrt to some sub-fields in AssessmentIssue field but since they haven't picked up previous payload version, they can just directly jump to implementing this(being more future proof).

How was this pull request tested?

Existing tests.
Manually tested ybd ui is not broken for assessment phase.

Does your PR have changes that can cause upgrade issues?

Component	Breaking changes?
MetaDB	Yes/No
Name registry json	Yes/No
Data File Descriptor Json	Yes/No
Export Snapshot Status Json	Yes/No
Import Data State	Yes/No
Export Status Json	Yes/No
Data .sql files of tables	Yes/No
Export and import data queue	Yes/No
Schema Dump	Yes/No
AssessmentDB	Yes/No
Sizing DB	Yes/No
Migration Assessment Report Json	Yes/No
Callhome Json	Yes/No
YugabyteD Tables	Yes/No
TargetDB Metadata Tables	Yes/No

[sanyamsinghal]

https://jenkins.dev.yugabyte.com/job/users/job/yb-voyager-testing/job/yb-voyager-testing-pipeline/4549/

[priyanshi-yb]

How are we populating MigrationComplexityExplanation, don't see any change related to that here?

[priyanshi-yb]

OR are we just adding the field but not sending the actual explanation as of this PR?

[sanyamsinghal]

oh right, that was a miss. Updated.

[priyanshi-yb]

LGTM!