[receiver/snmp] Add column and scalar OID metrics to resources that have scalar OID attributes (#25174)

**Description:** <Describe what has changed.>
- Added a new scalar_oid field to ResourceAttribtueConfigs to allow
Scalar OIDs to be used as resource attributes (on Column OID metrics)
- Added support for (Scalar OID only) resource attributes on Scalar OID
metrics as well.

**Link to tracking Issue:** 

#23373

**Testing:** 
- Valid and invalid configs using a scalar_oid resource attribute on
both scalar and column oid metrics
- Adding indexed metrics to resources with scalar_oid resource
attributes
- Adding scalar metrics to resources with scalar_oid resource attributes

**Documentation:** <Describe the documentation added.>
- Description of new scalar_oid field in ResourceAttributeConfig and
comments on new functions
- Description of new ResourceAttributes field on Scalar OID metrics

Author: kuiperda

.chloggen/feat_snmpreceiver-resource-attribute-updates.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: snmpreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Support scalar OID resource attributes
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [23373]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: Add column and scalar OID metrics to resources that have scalar OID attributes
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

receiver/snmpreceiver/README.md

@@ -81,8 +81,9 @@ Resource attribute configurations are used to define what resource attributes wi
 
 | Field Name           | Description                              | Value        |
 | --                   | --                                       | --           |
-| `oid`                  | Required if no `indexed_value_prefix`. This is the column OID in a SNMP table which will use the returned indexed SNMP data to create resource attribute values for unique resources. Metric configurations will reference these resource attribute configurations in order to assign metrics data to resources | string       |
-| `indexed_value_prefix` | Required if no `oid`. This is a string prefix which will be added to the indices of returned metric indexed SNMP data to create resource attribute values for unique resources. Metric configurations will reference these resource attribute configurations in order to assign metrics data to resources | string       |
+| `oid`                  | Required if no `scalar_oid` or `indexed_value_prefix`. This is the column OID in a SNMP table which will use the returned indexed SNMP data to create resource attribute values for unique resources. Metric configurations will reference these resource attribute configurations in order to assign metrics data to resources | string       |
+| `scalar_oid` | Required if no `oid` or `indexed_value_prefix`. This is the scalar OID which will return non-indexed SNMP data to create resource attribute values for unique resources. Metric configurations will reference these resource attribute configurations in order to assign metrics data to resources | string |
+| `indexed_value_prefix` | Required if no `scalar_oid` or `oid`. This is a string prefix which will be added to the indices of returned metric indexed SNMP data to create resource attribute values for unique resources. Metric configurations will reference these resource attribute configurations in order to assign metrics data to resources | string       |
 | `description`          | Definition of what the resource attribute represents  | string       |
 
 #### Attribute Configuration
@@ -125,6 +126,7 @@ Attribute configurations are used to define what resource attributes will be use
 | Field Name  | Description                                                    | Value                       | Default |
 | --          | --                                                             | --                          | --      |
 | `oid`       | The SNMP scalar OID value to grab data from (must end in .0).  | string                      |         |
+| `resource_attributes` | The names of the related resource attribute configurations, allowing scalar oid metrics to be added to resources that have one or more scalar oid resource attributes. Cannot have indexed resource attributes as values. | string[] | | 
 | `attributes` | The names of the related attribute enum configurations as well as the values to attach to this returned SNMP scalar data. This can be used to have a metric config with multiple ScalarOIDs as different datapoints with different attributue values within the same metric | Attribute              |    |
 
 #### ColumnOID Configuration