chore: add status page for block scheduler

[ashwanthgoli]

What this PR does / why we need it:

Adds a status page for block scheduler which can be accessed at GET /blockscheduler/status

It lists the following details:

• pending jobs ordered by priority
• in progress jobs ordered by start time
• partition lag, start and end offsets for pending partitions

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:
Added a test to generate an example status page which is skipped by default. Remove t.Skip() to generate and inspect the html file

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR