When parsing stacks we frequently encounter elided frames. The actual
stack line looks something like `...23 frames elided...`, which is
passed to `parseFuncName`, which of course is not parsable as a function
name. As a result, whenever this happens we get a useless panic like the
following:

```
panic: Failed to parse stack trace: parse function: no function found: "...23 frames elided..."
goroutine 1 [running]:
go.uber.org/goleak/internal/stack.getStackBuffer(0x1)
	/home/runner/go/pkg/mod/go.uber.org/goleak@v1.3.0/internal/stack/stacks.go:240 +0x65
go.uber.org/goleak/internal/stack.getStacks(0x1)
	/home/runner/go/pkg/mod/go.uber.org/goleak@v1.3.0/internal/stack/stacks.go:84 +0x3b
go.uber.org/goleak/internal/stack.All(...)
	/home/runner/go/pkg/mod/go.uber.org/goleak@v1.3.0/internal/stack/stacks.go:229
go.uber.org/goleak.Find({0xc0003ae880, 0x4, 0x4})
	/home/runner/go/pkg/mod/go.uber.org/goleak@v1.3.0/leaks.go:65 +0x1ea
```

This PR gracefully handles elided frames to prevent the panic.

Follow-up to #120, I accidentally merged the PR without waiting for all
tests to run, and missed that 1.20 tests are failing.

Lint is failing because of how we skip golangci-lint run in the action
and use the Makefile. Use the same logic as zap to skip lint.

Tests are failing on 1.20 as stack elision doesn't kick in for the test.
From 1.21 onwards, it does kick in. Rather than try to make the test
trigger stack elision on 1.20, let's bump the versions to 1.21 / 1.22.

This upgrades codecov CI action to version 4,
and uses the codecov token when uploading,
since tokenless uploading is no longer supported for some cases.

This upgrades codecov CI action to version 4,
and uses the codecov token when uploading,
since tokenless uploading is no longer supported for some cases.

This add explicit exemption for things we don't care about in errcheck
lint message.

The PR moves `isTraceStack` from the `tracestack_new.go` to
`options.go`. The file `tracestack_new.go` became unnecessary after #79.

This PR replaces the deprecated `GoDoc` links with new ones to `Go
Reference` in `README.md`.

See golang/go#49212 for details about the
deprecated `godoc`.
The badge is created at https://pkg.go.dev/badge/.

This adds an Option to run goleak when test runs fail.

Fixes #128.

someone at Uber unfortunately spent cycles trying to convert
VerifyTestMain call to VerifyNone(t) for individual cases only to find
out that it doesn't work well with t.Parallel().

Even though VerifyNone(t)'s documentation already says this, it might be
worth clarifying this in the README since the wording can make it sound
like calling VerifyTestMain() vs calling VerifyNone() at the end of
every single test case is completely identical in behavior.