Rename "implementation" to "frame type"

In #1275, there is confusion over the use of "Category" for the frame's implementation. I think the term "implementation" is a bit ambiguous. Historically (I at least) have avoided using it in the UI since I felt that users wouldn't know what that meant exactly. I think a more precise word that can be used both internally and in the UI could be "frame type". These frame types would be would be:

* Native (both C++ and Rust)
* JS Interpreter
* JS Baseline
* JS Ion
* Wasm
* asm.js (is this distinguised?
* Label

Then instead of an "implementation filter" we could have a "frame type filter" that would be:

* Combined - All frames are shown
* Native - C++, Rust, and native-like labels will be shown
* JS - All JS engine frames will be shown, plus relevant labels

I think in some conversation earlier, mstange had some nice ideas on how to know which labels are native or JS. I don't really recall what the exact rule was.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-66)