Current mechanism to deprecate config options is implemented in a hacky
way in `main.cpp` and doesn't account for existing
`db::config/boost::po` API controlling lifetime of config options, hence
it's being replaced in this PR by adding yet another `value_status`
enumerator: `Deprecated`, so that deprecation of config options is
controlled in one place in `config.cc`,i.e. when specifying config options.
Motivation: https://docs.google.com/document/d/18urPG7qeb7z7WPpMYI2V_lCOkM5YGKsEU78SDJmt8bM/edit?usp=sharing
With this change, if a `Deprecated` config option is specified as
1. a command line parameter, scylla will run and log:
```
WARN 2023-11-25 23:37:22,623 [shard 0:main] init - background-writer-scheduling-quota option ignored (deprecated)
```
(Previously it was only a message printed to standard output, not a
scylla log of warn level).
2. an option in `scylla.yaml`, scylla will run and log:
```
WARN 2023-11-27 23:55:13,534 [shard 0:main] init - Option is deprecated : background_writer_scheduling_quota
```
Fixes#15887
Incorporates dropped https://github.com/scylladb/scylladb/pull/15928Closesscylladb/scylladb#16184
5fd30578d7