Issue 85: Add infrastructure for analytical solutions in R

[seabbs]

Description

This PR partially closes #85 by adding infrastructure in R for introducing analytical solutions. It also adds skeletons for the current solutions but does not add the analytical solutions themselves.

Checklist

• [x] My PR is based on a package issue and I have explicitly linked it.
• [x] I have included the target issue or issues in the PR title in the for Issue(s) issue-numbers: PR title
• [x] I have read the contribution guidelines.
• [x] I have tested my changes locally.
• [x] I have added or updated unit tests where necessary.
• [x] I have updated the documentation if required.
• [x] My code follows the established coding standards.
• [x] 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[bot]]

Codecov Report

Attention: Patch coverage is 90.47619% with 6 lines in your changes missing coverage. Please review.

Project coverage is 98.06%. Comparing base (5c23d7a) to head (9a48117). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
R/primary_censored_dist.R	86.04%	6 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #87 +/- ## ========================================== - Coverage 99.67% 98.06% -1.62% ========================================== Files 8 10 +2 Lines 310 362 +52 ========================================== + Hits 309 355 +46 - Misses 1 7 +6 ```

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[github-actions[bot]]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 86a9695e0578d7fac31b2bed522fd50107988e41 is merged into main:

• :heavy_check_mark:cmdstan_fit_gamma: 7.66s -> 7.71s [-0.04%, +1.25%]
• :heavy_check_mark:cmdstan_fit_lognormal: 1.71s -> 1.7s [-1.91%, +0.41%]
• :exclamation::snail:dprimarycensoreddist_expgrowth: 2.08ms -> 2.36ms [+12.43%, +14.82%]
• :exclamation::snail:dprimarycensoreddist_weibull: 1.99ms -> 2.27ms [+12.54%, +14.89%]
• :exclamation::snail:fitdistdoublecens_gamma: 665ms -> 675ms [+0.34%, +2.52%]
• :heavy_check_mark:fitdistdoublecens_normal: 558ms -> 565ms [-1.59%, +4.03%]
• :exclamation::snail:pprimarycensoreddist_expgrowth: 41.6ms -> 51.1ms [+21.8%, +23.73%]
• :exclamation::snail:pprimarycensoreddist_lnorm: 37.7ms -> 47.6ms [+25.5%, +27.2%] Further explanation regarding interpretation and methodology can be found in the documentation of touchstone.

[github-actions[bot]]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 9581170494bb3c7d8dd93b91db3326a6c1d54960 is merged into main:

• :heavy_check_mark:cmdstan_fit_gamma: 7.62s -> 7.63s [-0.65%, +0.88%]
• :heavy_check_mark:cmdstan_fit_lognormal: 1.64s -> 1.62s [-5.79%, +3.41%]
• :exclamation::snail:dprimarycensoreddist_expgrowth: 1.93ms -> 2.8ms [+43.1%, +46.6%]
• :exclamation::snail:dprimarycensoreddist_weibull: 1.87ms -> 2.74ms [+43.99%, +49.26%]
• :exclamation::snail:fitdistdoublecens_gamma: 657ms -> 673ms [+1.77%, +2.93%]
• :exclamation::snail:fitdistdoublecens_normal: 547ms -> 559ms [+1.84%, +2.68%]
• :exclamation::snail:pprimarycensoreddist_expgrowth: 37.6ms -> 46.1ms [+20.23%, +25.2%]
• :exclamation::snail:pprimarycensoreddist_lnorm: 34.2ms -> 42.6ms [+22.43%, +26.37%] Further explanation regarding interpretation and methodology can be found in the documentation of touchstone.

[seabbs]

I'm fairly horrified by what I had to do here to get this working but despite that I think its the most sensible approach that retains modularity

[github-actions[bot]]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 596c03f5db9d7029ffbf088f087970499c7919a3 is merged into main:

• :heavy_check_mark:cmdstan_fit_gamma: 7.7s -> 7.75s [-0.23%, +1.69%]
• :heavy_check_mark:cmdstan_fit_lognormal: 1.65s -> 1.63s [-5.54%, +3.22%]
• :exclamation::snail:dprimarycensoreddist_expgrowth: 1.95ms -> 2.34ms [+17.38%, +22.82%]
• :exclamation::snail:dprimarycensoreddist_weibull: 1.87ms -> 2.27ms [+18.7%, +24.27%]
• :exclamation::snail:fitdistdoublecens_gamma: 665ms -> 678ms [+0.92%, +3.01%]
• :exclamation::snail:fitdistdoublecens_normal: 557ms -> 562ms [+0.65%, +1.47%]
• :exclamation::snail:pprimarycensoreddist_expgrowth: 37.5ms -> 45.4ms [+19.21%, +23.35%]
• :exclamation::snail:pprimarycensoreddist_lnorm: 34.4ms -> 42.2ms [+20.52%, +25.38%] Further explanation regarding interpretation and methodology can be found in the documentation of touchstone.

[seabbs]

Test gaps are due to the current lack of analytical solutions so I think this is good to go.