Avoid string.Format allocations by ProfilingViewEngine when profiler is not enabled.

[nzdev]

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes

Description

Each time ProfilingViewEngine.FindView and ProfilingViewEngine.GetView is called (each time a view is used) the ProfilingViewEngine calls string.Format for a log message as part of profiling. However, if Umbraco is not in debug mode, this is unnecessary as the IProfiler will be a NoOp and will discard the formatted string, however this formatted string is still allocated.

This PR adds a IsEnabled property to IProfiler, so the string.Format allocations can be avoided when the IProfiler is not enabled.

How to test?
Check that IProfiler.Step is not called when IProfiler is not enabled.

[github-actions]

Hi there @nzdev, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
• The level of performance for this contribution is the same or improved
• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
• If this is a new feature, Umbraco HQ provided guidance on the implementation beforehand
• 💡 The contribution looks original and the contributor is presumably allowed to share it

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If you realize that you might want to make some changes then you can do that by adding new commits to the branch you created for this work and pushing new commits. They should then automatically show up as updates to this pull request.

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[georgebid]

Hey @nzdev, thanks a lot for your PR 😄 someone on the Core Collaborators team will review this soon!

[JasonElkin]

Thanks @nzdev!