Reuse existing scope ids in register_user_scopes

[Azkellas]

Checklist

• I have read the Contributor Guide
• I have read and agree to the Code of Conduct
• I have added a description of my changes and why I'd like them included in the section below

Description of Changes

Currently, GlobalProfiler::register_user_scopes requires users to track the scopes details to avoid bad memory leaking. This is effectively asking the users to keep their own ScopeCollection when the data is already stored internally.

I'm aware that the GlobalProfiler scope_collection is private and the design is here intentionally but the comment mentions the frame views and, as far as I know, external applications can't create frames without first creating the ids.

To make the api nicer for external applications, I make register_user_scopes first check if the scope name is already in the collection, and only create a new id if this is the first time encountering the scope label. Another solution would be to make the scope collection accessible (read only) from outside.

Note: I'm not super familiar with the puffin codebase and overall architecture, I might be missing some subtleties.

[Azkellas]

See Wumpf/wgpu-profiler#104 for what motivated this pull request.
wgpu-profiler outputs gpu timings to puffin. The current implementation does not cache scope ids, which leads to massive leakage, and adding a cache is an unnecessary burden to the end user.

[Azkellas]

On a side note, this is out of scope for this PR and probably for puffin as well, but since the GPU timings are available late, the current solution is to add another puffin profiler to app using gpu timings with puffin.

Is there a way to retrospectively add scopes to a previous frame or would that be too much of a change in design / not the puffin philosophy?

[Wumpf]

makes sense to me. @emilk any chance this could be in a patch release?

[emilk]

any chance this could be in a patch release?

Isn't this a breaking change? :/

[Wumpf]

hmmmmmm I suppose technically it is since the returned ids are different