What kind of change does this PR introduce?
Enhancement

What is the current behavior?
ApiException call stack starts with something like:

   at Refit.RequestBuilderImplementation.<>c__DisplayClass14_0`2.<<BuildCancellableTaskFuncForMethod>b__0>d.MoveNext()

What is the new behavior?
ApiException call stack starts with something like:

   at Refit.Implementation.Generated.RefitTestsIGitHubApi.<global::Refit-Tests-IGitHubApi-CreateUser>d__29.MoveNext()

Useful for observability to know which request method failed.

What might this PR break?
Folks that depend on the existing stack trace.

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Other information:
👋