add emptyDir agent and CR volume for SA receiver collectd config

[rmfitzpatrick]

In cases like openshift's default SecurityContextConstraints when the agent is set to have a read-only root filesystem, collectd monitor use isn't possible without having a declared volume mount for its run directory:

error	collectd/monitorcore.go:126	Could not render collectd plugin config	{"kind": "receiver", "name": "smartagent/collectd/mysql", "data_type": "metrics", "error": "failed to create collectd config dir at /usr/lib/splunk-otel-collector/agent-bundle/run/collectd/monitor-smartagentcollectdmysql/managed_config: mkdir /usr/lib/splunk-otel-collector/agent-bundle/run/collectd/monitor-smartagentcollectdmysql: read-only file system", "monitorID": "smartagentcollectdmysql", "monitorType": "collectd/mysql", "path": "/usr/lib/splunk-otel-collector/agent-bundle/run/collectd/monitor-smartagentcollectdmysql/managed_config/20-mysql.smartagentcollectdmysql.conf"}

[rmfitzpatrick]

It'd probably make sense to add these to the CR deployment as well.

edit: updated.