Doc.: Operation string matching semantics not specified

The page section currently at https://istio.io/latest/docs/reference/config/security/authorization-policy/#Operation doesn't specify the semantics of the strings in the various fields of Operation.

Although an example _implies_ that "`*`" is a wildcard character, there is no normative (e.g., non-example) text that _specifies_ exactly how the given string are interpreted.

(The documentation should be sufficient to answer questions such as:
- Are there any other wildcard characters?
- Is there an escape character (or any other construct) for literally matching a "`*`"?
- Can there be multiple uses of wildcarding in a given match string? (Some Istio uses of "`*`" in host names can appear only once.)
- What exactly are the semantics of "`*`"? Does it always just match zero to N arbitrary characters? Or does it do anything special when adjacent (or non-adjacent) to "`/`" or "`.`" characters in a path- or host-match string?

)