Automate reference docs for commandline flags and env vars

检查现有的 CRD 参考文档生成工作流，以及手动生成的 HBase 命令行和环境变量参考页面。然后，将 operators 的帮助输出与 issue 中描述的 build.rs 和 clap 解析器集成进行比较，包括子命令是否需要单独处理。完成的标准是选择并实现一种易于维护的生成方式，在不手写 flag 和环境变量列表的情况下生成可用的参考页面。

Problem: Currently we have hand written docs in every operator about commandline flags and environment variables read by the operators. This is difficult to maintain and in some places it is already out of date. Like the CRD references, it would be good to generate this to reduce maintenance burden.

Cheapo variant A: dump the help page

The help pages of the operators actually already reference all the flags (obviously) and also most env vars (some would need to be added through clap, that is easy though). We already do this for stackablectl. It isn't pretty, the formatting is actually quite ugly.

By default the help doesn't show help for subcommands. Maybe we have to call each subcommand individually (or maybe we just show the help for run).

Slightly more involved variant B: generate man page, convert to adoc

There is https://github.com/clap-rs/clap/tree/master/clap_mangen to generate man pages from clap.

We could use pandoc to convert the man page to an adoc file:

pandoc -s -t asciidoc example.man -o example.adoc

And use that as our reference page.

This is a bit annoying to implement because the build.rs file has to include the clap parser definition too. Also I am unsure about the pandoc converted adoc page, I am not sure if the styling can be changed or how easily it can be done.

For reference (currently manually generated):
https://docs.stackable.tech/home/stable/hbase/reference/commandline-parameters/
https://docs.stackable.tech/home/stable/hbase/reference/environment-variables/