[Feature] ability group outputs in the trace viewer

[scott-au]

the show steps/fixtures in the trace is certainly a nice feature released in 1.34 - grouping all the associated actions makes a trace file easier to go through.

is there any chance we could also have some sort of mechanism that allows us to group actions together in a similar fashion for users not using playwright test.

[DetachHead]

i looked into this and would like to have a go at implementing it. it seems straightforward, looks like trace events just need the parentId field in the metadata.

i will probably make a step context manager that works the same as the test.step method in @playwright/test