Merge #11191: RPC: Improve help text and behavior of RPC-logging.

Merge #11191: RPC: Improve help text and behavior of RPC-logging.

c60c49b Improve help text and behavior of RPC-logging (Akio Nakamura)

Pull request description:

  1. It is allowed `libevent` logging to be updated during runtime,
    but still described that restriction in the help text.
    So we delete these text.
  2. Add a descrption about the evaluation order of `<include>` and
    `<exclude>` to clarify how debug loggig categories to be set.
  3. Add a description about the available logging category `"all"`
    which is not explained.
  4. Add `"optional"` to the help text of `<include>` and `<exclude>`.
  5. Add missing new lines before `"Argument:"`.
  6. `"0"`,`"1"` are allowed in both array of `<include>` and `<exclude>`.
    `"0"` is **ignored** and `"1"` is treated **same as** `"all"`.
    It is confusing, so forbid them.
  7. It always returns all logging categories with status.
    Fix the help text to match this behavior.

Tree-SHA512: c2142da1a9bf714af8ebc38ac0d82394e2073fc0bd56f136372e3db7b2af3b6746f8d6b0241fe66c1698c208c124deb076be83f07dec0d0a180ad150593af415