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

Summary:
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

Backport Core PR11191
https://github.com/bitcoin/bitcoin/pull/11191/

Depends on D3684

Test Plan:

make check
./bitcoind
./bitcoin-cli help logging

Changes should be reflected in the help text

Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: Fabien, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D3699