Add some extra HTTP options

[thegreatco]

This PR covers 2 features:

1. Add a setting to tweak the response buffer. When using the rss feed plugin, some responses are too big for the default buffer. If the device has the memory, the user can increase the buffer size in the Device Settings modal
2. Some HA deployments (like mine) require auth on the rss_proxy endpoint (which is good practice in general), so we now add the request_headers.Authorization key to the rss feed code's http_request.get, populated with ESPHomeDesigner's long lived HA access token.

Tests for both changes are in-progress.

Note: This PR does depend on #396. If/when that is merged, I will rebase this branch onto main before trying to merge.

[koosoli]

Thanks for the PR. I know it is still draft but could you please rebase/update this branch onto the latest main, resolve the generated frontend asset conflicts, rebuild the frontend/dist output if needed. I think then it will be a valuable addition :-)