cmd/errtrace: Built-in list of exclusions

[abhinav]

From:

          maybe a feature request for future, should we have a set of default opt-outs inbuilt, like don't wrap `io.EOF` when being returned from `Read`? (It's not perfect, but seems like it's never correct to wrap an EOF error from `Read`)

Originally posted by @prashantv in #57 (comment)

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We should consider a built-in list of ignores.
These will be pretty simplistic since we don't use type information (yet).
We already have an exclusion for Unwrap() error methods.

This issue is to track both, the feature and what should be in the exclusions initially:

• io.EOF returned from a Read() (int, error) method

[Nico-Hab]

I just ran into this and wondered why IO code stopped functioning with my Readers, after running the CLI instrumentation tool. This would be very helpful, even if it's not perfect