feat(upload): auto-upload chunks every hour (#5)

### Summary

 This commit adds the Kconfig settings to enable auto-upload of chunks.
 The default interval is 1 hour, but can be changed in the Kconfig
 `CONFIG_MEMFAULT_HTTP_PERIODIC_UPLOAD_INTERVAL_SECS`. While this application
 relies on the user configuring the wifi connection through the shell,
 it is a sane default to assume a connection has been made.

 ### Test Plan

 Flashed esp32s3, saw auto-upload after an hour.

Author: gminn

prj.conf

@@ -42,6 +42,7 @@ CONFIG_MEMFAULT=y
 CONFIG_MEMFAULT_LOGGING_ENABLE=y
 CONFIG_MEMFAULT_HTTP_ENABLE=y
 CONFIG_MEMFAULT_TLS_CERTS_USE_DER=y
+CONFIG_MEMFAULT_HTTP_PERIODIC_UPLOAD=y
 
 # Additional network configuration for Memfault features
 CONFIG_DNS_RESOLVER=y