[DocDB] AutoFlags should provide the capability to enable flags on Install scenarios only, but not upgrade

[rthallamko3]

Jira Link: DB-6229

Description

AutoFlags should provide the capability to enable flags on Install scenarios only, but not upgrade (so as to lower the risk of new big features like PackedRow,AutomaticTabletSplitting from being enabled automatically without explicit Customer knowledge, during an upgrade).

Approach: Add a new enum kNewInstallsOnly to AutoFlagClass.

YB_DEFINE_ENUM(
    AutoFlagClass,
    // Adds/modifies format of data sent over the wire to another process within the universe. No
    // modification to persisted data.
    ((kLocalVolatile, 1))
    // Adds/modifies format of data sent over the wire or persisted and used within the universe.
    ((kLocalPersisted, 2))
    // Adds/modifies format of data which might be used outside the universe.
    // Example of external processes: XCluster and CDCServer.
    ((kExternal, 3)));

Requirements

• The new enum kNewInstallsOnly would restrict the set of autoflags that will be promoted during upgrade, to exclude the ones tagged as kInstallsOnly.
• If an AutoFlag is tagged as kNewInstallsOnly, xCluster setup needs to be blocked if the set of auto flags are inconsistent at the source and target.

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