Issue #69: Add check_truncation

[seabbs]

Description

This PR closes #69. It adds a heuristic function to check if the specified truncation is appropriate. It does this by looking at the max delay for a given observation time and throws a message if this the observation time is greater by some (user settable multiplier). This is used in fitting functions to help make sure users get efficient fitting. This PR also renames pcd_as_cmdstan_data to pcd_as_stan_data to better fit the package.

Checklist

• My PR is based on a package issue and I have explicitly linked it.
• I have included the target issue or issues in the PR title in the for Issue(s) issue-numbers: PR title
• I have read the contribution guidelines.
• I have tested my changes locally.
• I have added or updated unit tests where necessary.
• I have updated the documentation if required.
• My code follows the established coding standards.
• I have added a news item linked to this PR.
• I have reviewed CI checks for this PR and addressed them as far as I am able.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.35%. Comparing base (44f9871) to head (62762c0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #120      +/-   ##
==========================================
+ Coverage   99.29%   99.35%   +0.05%     
==========================================
  Files          10       10              
  Lines         427      463      +36     
==========================================
+ Hits          424      460      +36     
  Misses          3        3              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[seabbs]

LGTM (self-review)