[Saved Objects] Investigate Cohesion and De-coupling Improvements for Repository & Security Extension

[jeramysoucy]

To be considered after PR 142878 has merged.

Description

During review of PR 142878, it was identified that the cohesion/coupling between the Saved Objects Repository and the Saved Objects Security Extension should be investigated and improved.

To be considered...

• [Saved Objects] Combine Check & Enforce in Security Extension #147045

• [Saved Objects] Migrate audit logging into the security extension #147048

• [Saved Objects] Migrate authorization & audit logic into the security extension #147049

It will be important to keep in mind the current flexibility we have in the current implementation which lends to improved performance and authz granularity over the previous wrapper implementations (such as reduced number of queries to elasticsearch, and per-object/type/space checks), and to refrain from compromising this in any updates.

[elasticmachine]

Pinging @elastic/kibana-security (Team:Security)

[jeramysoucy]

Migration of authorization logic and audit logging is underway in this PR.