docs: integrate the roclet to igraph proper

[maelle]

Fix #2899

[maelle]

I instructed Claude to add caching through that approach; igraph.r2cdocs has a dependency on memoise.

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if db199d7 is merged into main:

• ✔️as_adjacency_matrix: 199ms -> 198ms [-0.81%, +0.18%]
• ✔️as_biadjacency_matrix: 204ms -> 204ms [-0.5%, +0.2%]
• ✔️as_data_frame_both: 193ms -> 191ms [-2.28%, +0.81%]
• ❗🐌as_long_data_frame: 165ms -> 166ms [+0.09%, +1.3%]
• ✔️es_attr_filter: 208ms -> 208ms [-0.41%, +0.41%]
• ✔️graph_from_adjacency_matrix: 238ms -> 239ms [-0.25%, +0.6%]
• ✔️graph_from_data_frame: 217ms -> 218ms [-1.16%, +1.76%]
• ✔️vs_attr_filter: 205ms -> 205ms [-0.71%, +0.93%]
• ✔️vs_by_name: 176ms -> 176ms [-0.67%, +0.59%]
  Further explanation regarding interpretation and methodology can be found in the documentation.

[maelle]

The current code has deps on various packages. Some of them we can remove like tibble or purrr, some of them we have to use (treesitter). Before I go about adding fixes / workarounds, I'd like to confirm we want to move the roclet infrastructure into this package.

'::' or ':::' imports not declared from:
     ‘fs’ ‘purrr’ ‘roxygen2’ ‘tibble’ ‘treesitter’ ‘treesitter.r’ ‘xml2’

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 63f3088 is merged into main:

• 🚀as_adjacency_matrix: 175ms -> 175ms [-0.55%, -0.02%]
• ✔️as_biadjacency_matrix: 193ms -> 195ms [-0.83%, +2.86%]
• ✔️as_data_frame_both: 197ms -> 197ms [-0.58%, +0.46%]
• ✔️as_long_data_frame: 159ms -> 159ms [-0.48%, +0.48%]
• ✔️es_attr_filter: 187ms -> 187ms [-0.5%, +0.42%]
• ✔️graph_from_adjacency_matrix: 212ms -> 212ms [-0.45%, +0.35%]
• ✔️graph_from_data_frame: 215ms -> 214ms [-1.15%, +0.22%]
• ✔️vs_attr_filter: 225ms -> 225ms [-0.53%, +0.46%]
• ✔️vs_by_name: 206ms -> 206ms [-0.56%, +0.29%]
  Further explanation regarding interpretation and methodology can be found in the documentation.