SAC: Fix sampling rate floating point accuracy edge cases

[megies]

What does this PR do?

Fixes reading some SAC files that suffer from floating point accuracy issues with their sampling interval stored in single precision.

Makes it opt-out, so the rounding can be deactivated and also it will show a warning if the rounding actually changed things during reading SAC.

Why was it initiated? Any relevant Issues?

fixes #3408

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[jkmacc-LANL]

Looks good, thank you! All these changes just to round a float 😄

[megies]

Looks good, thank you! All these changes just to round a float 😄

🤣 It's like always, making the change would be a one-liner and about one minute of work, but thinking it through, documenting it properly, letting people know when it happens by showing a warning and properly testing both the actual change and the warning as well is 99% of the work and makes it a long task. That's how you see all these software projects from publications that are unusable to other people but fast to get a citation 😜

I do believe it's one of our strong points though, to be robust, reliable and transparent. Even if it slows us down these days (well more people dedicating time would help too 🤣).

[jkmacc-LANL]

Thank you!