Scope ScriptJwtBearerHandler logs to system-only

[jviau]

Issue describing the changes in this PR

resolves #10532

Pull request checklist

IMPORTANT: Currently, changes must be backported to the in-proc branch to be included in Core Tools and non-Flex deployments.

• Backporting to the in-proc branch is not required
  • Otherwise: Link to backporting PR
• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

Additional information

As part of our changes to DI in the out-of-proc host many components now resolve loggers from the job host, which includes customer logs. This was intentional and what we wanted for the most part. However, we have identified that JwtBearerHandler for script auth produces noisy logs which are distracting to have in customer logs. This PR addresses this by ensuring the JwtBearerHandler gets loggers from the parent scope only. This is done as follows:

1. Introduce a new ISystemLoggerFactory interface which is used to create loggers from system-only providers.
   • This is a mere wrapper around ILoggerFactory.
   • This is registered as a singleton in the WebHost, meaning its exact instance will be forwarded to the JobHost.
2. Introduce ScriptJwtBearerHandler, which inherits JwtBearerHandler. This now imports ISystemLoggerFactory instead of ILoggerFactory.

[jviau]

/azp run host.public

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[fabiocav]