Feature Request: Custom Page Cache Storage Location

### Impacted plugin

Boost

### What

I would like to set a custom location for the page cache created by the Boost plugin.

### How

**Presently**: Boost creates a _boots-cache_ directory in the _wp-content_ directory and stores all page cache in there.

**Want**: I would like to be able to set a custom location for the page cache directory created by the Boost plugin; either via the admin interface, or _wp-config.php_.

**Why**: I am hosting my WordPress website on a Linux VM which has fast temporary storage. The temporary storage is limited in size, because it is part of the storage drive of the host system, but it is much faster than the persistent storage. In addition, the temporary storage is free and billable IOPs do not count towards it.

**Workaround**: For the time being I have created a boost-cache symlink, in wp-content, pointing to a directory on the temporary/fast drive.

Start by locating the Boost plugin code that creates the boots-cache directory under wp-content, then inspect its admin interface and wp-config.php handling. Done means the page-cache location can be configured through one supported path and caching still works when the directory is on temporary storage.

Written by the indexing model from the issue text.