[Doc][Parameter] Improve built-in parameter usage and combination documentation

[fatmanverse]

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• I had searched in the issues and found no similar documentation request or DSIP.

Description

The built-in parameter documentation lists the available system.* variables and some time expressions, but it does not explain how each parameter behaves across scheduled, complement, and manual runs. It also lacks complete usage examples for the time-expression functions and does not describe how named parameters ${...} and time expressions $[...] are resolved when they are combined.

The documentation should:

• Explain the value and usage of every current system.* built-in parameter.
• Clarify the benchmark time used by $[...] expressions.
• Document date arithmetic, calendar boundary functions, and timestamp(...).
• Describe the resolution order for ${...} and $[...].
• Add Shell, SQL, custom parameter, and downstream parameter examples.
• Keep the English and Chinese documentation and navigation in sync.

This is an incremental documentation improvement and does not change public interfaces or runtime behavior.

Documentation Links

• https://dolphinscheduler.apache.org/en-us/docs/dev/user_doc/guide/parameter/built-in.html
• https://dolphinscheduler.apache.org/zh-cn/docs/dev/user_doc/guide/parameter/built-in.html

Are you willing to submit a PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project Code of Conduct.