fix(inputs.ping): Warn on using timeout parameter for native method

[WZH8898]

Summary

Fix issue where the timeout parameter was ignored when using method = "native".

The native pinger uses a global timeout, so this change computes an effective
runtime timeout based on:

• configured timeout
• send interval between packets
• packet count

The computed timeout is also capped by the configured deadline.

Unit tests have been added for the timeout calculation.

Checklist

• No AI generated code was used in this PR
• AI generated code used in this PR follows the InfluxData Policy on AI-Generated Code Contributions

Related issues

resolves #18395

[srebhan]

@WZH8898 please restore the PR description template, especially the AI section, so we can review your contribution!

[WZH8898]

@WZH8898 please restore the PR description template, especially the AI section, so we can review your contribution!

Thanks! I've restored the PR template and added the AI checklist section.
Please let me know if anything else needs to be adjusted.

[srebhan]

@WZH8898 to be honest I don't like the approach too much as it has too many assumptions. How about rather than trying to guess ask the user to use the deadline configuration option instead as this is what is used already? I.e. if you see timeout to be set with the native method, you should error out (or warn) in Init() that this parameter is not used for the method and what to do instead. Maybe also add some documentation to the README?

[WZH8898]

@WZH8898 to be honest I don't like the approach too much as it has too many assumptions. How about rather than trying to guess ask the user to use the deadline configuration option instead as this is what is used already? I.e. if you see timeout to be set with the native method, you should error out (or warn) in Init() that this parameter is not used for the method and what to do instead. Maybe also add some documentation to the README?

Thanks for the suggestion! I've updated the implementation to warn when timeout is used with the native method and documented the behavior in the README.
Please let me know if further adjustments are needed.

[telegraf-tiger]

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[srebhan]

Thanks @WZH8898! Some more small comments...

[srebhan]

Log always is non-nil at runtime. If you see a panic here it's because the tests do not define Log which is a bug and should be fixed by setting the logger in the test!

[srebhan]

Please keep the newline.

[srebhan]

Suggested change

	## the "-W" option of the ping command. This setting is used by the "exec"
	## method only.
	## the "-W" option of the ping command (for "exec" method only)

[srebhan]

Suggested change

	## If set, the total ping deadline, in seconds. Operates like the "-w"
	## option of the ping command. Use this option to control timeout behavior
	## when using the "native" method.
	## If set, the total ping deadline, in seconds. Operates like the "-w"
	## option of the ping command. Use this option to control timeout behavior
	## when using the "native" method.