Add HTML pages to view tenants with overrides

[yvrhdn]

What this PR does:
Changes /status/overrides and /status/overrides/{tenant} to HTML page which are nicer and easier to use.

Examples:

/status/overrides with user-configurable overrides disabled

/status/overrides/{tenant} with user-configurable overrides disabled

/status/overrides with user-configurable overrides enabled

/status/overrides/{tenant} with user-configurable overrides enabled

Which issue(s) this PR fixes:
Fixes #

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[knylander-grafana]

Doc update looks good.

[mdisibio]

Tested most of this locally and LGTM. One thing I noticed is that when browsing to a non-existent tenant like /status/overrides/doesnotexist it prints the inherited settings from tenant * as expected - but is there a way to indicate that it's using the defaults and not configured specifically? Not a blocker, just curious. Also left a few nits for things that I think would improve readability. Non-blocking.

[mdisibio]

nit: Can this be simplified? Either by using *tenantsPageTenant or making use of how tenants[tenant] will return an uninitialized struct (with HasRunTimeOverrides=false)

[yvrhdn]

Tested most of this locally and LGTM. One thing I noticed is that when browsing to a non-existent tenant like /status/overrides/doesnotexist it prints the inherited settings from tenant * as expected - but is there a way to indicate that it's using the defaults and not configured specifically? Not a blocker, just curious. Also left a few nits for things that I think would improve readability. Non-blocking.

I gave this a shot and it gets a bit complicated because a tenant can be using its own runtime overrides, the wildcard (*) or the default overrides.

tempo/modules/overrides/runtime_config_overrides.go

Lines 484 to 498 in 21fde18

	func (o *runtimeConfigOverridesManager) getOverridesForUser(userID string) *Overrides {
	if tenantOverrides := o.tenantOverrides(); tenantOverrides != nil {
	l := tenantOverrides.forUser(userID)
	if l != nil {
	return l
	}
	l = tenantOverrides.forUser(wildcardTenant)
	if l != nil {
	return l
	}
	}
	return o.defaultLimits
	}

I added a text line that tells you where it found the overrides, I hope this is clear enough.

If a tenant has its own runtime overrides:

If a tenant does not have its own runtime overrides, but we have * overrides:

If neither is set and we fall back to the overrides.defaults configuration: