InfluxDB component improvements (#8633)

* Allow reporting some state attributes as tags to InfluxDB

Some state attributes should really be tags in InfluxDB. E.g.
it is helpful to be able to group by friendly_name, or add a custom
attribute like "location" and group by that. Graphs in Grafana are much
easier to read when friendly names are used, and not node ids.

This commit adds an optional setting to InfluxDB config:
'tags_attributes'. Any attribute on this list will be reported as tag
and not as field to InfluxDB.

* Allow overriding InfluxDB measurement for each reported item separately

Bundling all items with the same "unit of measurement" together does not
always makes sense. For example, both "relatively humidity" and "battery
level" are reported as "%", but I'd rather see them as separate
measurements in InfluxDB. This commit allows for 'influxdb_measurement'
attribute. When set on node, it will take precedence over the global
'override_measurement' and component-specific 'unit_of_measurement'.

* Minor updates to InfluxDB component improvements, as suggested by
@MartinHjelmare.

* Moved per-component config from 'customize' into 'influxdb'
configuration section. The following three sub-sections were added:
'component_config', 'component_config_domain' and
'component_config_glob'. The sole supported per-component attribute
at this point is 'override_measurement'.

* Lint

* Fixed mocked entity_ids in InfluxDB tests to be in domain.entity_id
format, to satisfy EntityValues requirements.

* Added tests for new InfluxDB configuration parameters

* Fixes to some docstrings