Add stack support

[dmcgowan]

Adds a new stack package which provides a stack error type. This is based off the stack from the archived pkg/errors package and buildkit's util/stack.

Differences...

• Directly serializable and registered with typeurl. Does not rely on protobuf generation or registration. The additional control over the marshal/unmarshal allows an efficient and single error object to be used.
• Does not wrap errors, instead relies on latest support in Go for multi-errors with the Unwrap() []error interface. This allows stacks to ride next to errors without changing their error structure. Introduced a "collapsible" interface to avoid outputting the stack errors unless the %+v option is given.
• Simple helper interface using contexts with no global map
• Uses runtime.CallerFrames to account for inlined functions instead of the "discourage" runtime.FuncForPC. See https://pkg.go.dev/runtime#Callers