Missing fields description for table `log_link_visit_action` in the Database schema reference

Nobody has claimed this yet.

## Page URL
https://developer.matomo.org/guides/database-schema#visit-actions (Chapiter Visit Actions)

## What is missing?
Many fields are missing in table `log_link_visit_action`:
| Field | Type | Nullable | Key | More info |
| -- | -- | -- | -- | -- |
| idvisit | bigint unsigned | NO | MUL | Sure this is the left part of the link 😉 |
| custom_float | double | YES | | No idea what it can be... Maybe the value in case of events with value? |
| idpageview | char(6) | YES | | Easy to understand, but not described in the doc |
| search_cat | varchar(200) | YES | | Used for search tracking |
| search_count | int unsigned | YES | | Used for search tracking |
| idaction_event_action | int unsigned | YES | | Easy to understand, but not described in the doc |
| idaction_event_category | int unsigned | YES | | Easy to understand, but not described in the doc |
| idaction_content_interaction | int unsigned | YES | | In case of **Contents** core plugin activation |
| idaction_content_name | int unsigned | YES | | In case of **Contents** core plugin activation |
| idaction_content_piece | int unsigned | YES | | In case of **Contents** core plugin activation |
| idaction_content_target | int unsigned | YES | | In case of **Contents** core plugin activation |

Also, `custom_var_k*` columns are described, whereas it is advised to disable the **CustomVariables** plugin, but `custom_dimension_*` columns are described, whereas it is advised to enable the **CustomDimensions** plugin.

Start with the database schema reference page at developer.matomo.org/guides/database-schema#visit-actions, focusing on the Visit Actions section and table log_link_visit_action. Verify the listed fields and plugin guidance against the schema and related documentation, then document each missing field and correct the CustomVariables and CustomDimensions descriptions.

Written by the indexing model from the issue text.