[receiver/vcenter] Adds New Packet Dropped Rate Metric for VMs (#32930)

**Description:** <Describe what has changed.>
Adds new default disabled (with Warning log for default enabled on next
release) metric `vcenter.vm.network.packet.drop.rate` for Virtual
Machines.

This metric makes use of the `droppedRx` and `droppedTx` Network
performance metrics detailed
[here](https://vdc-repo.vmware.com/vmwb-repository/dcr-public/d1902b0e-d479-46bf-8ac9-cee0e31e8ec0/07ce8dbd-db48-4261-9b8f-c6d3ad8ba472/network_counters.html)
for Virtual machines. This would use the same metric attributes as the
other VM packet metrics and closely match
`vcenter.vm.network.packet.rate` in every other way.

**Link to tracking Issue:** <Issue number if applicable>
#32929 

**Testing:** <Describe what testing was performed and which tests were
added.>
Unit/integration tests updated and tested. Local environment tested.

**Documentation:** <Describe the documentation added.>
New documentation generated based on the metadata.

.chloggen/feat_vcenter-vm-add-packet-drop-metric.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: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: vcenterreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Adds inititially disabled packet drop rate metric for VMs."
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [32929]
+
+# (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:
+
+# 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/vcenterreceiver/documentation.md

@@ -508,6 +508,23 @@ The memory utilization of the VM.
 | ---- | ----------- | ---------- |
 | % | Gauge | Double |
 
+### vcenter.vm.network.packet.drop.rate
+
+The rate of transmitted or received packets dropped by each vNIC (virtual network interface controller) on the virtual machine.
+
+As measured over the most recent 20s interval.
+
+| Unit | Metric Type | Value Type |
+| ---- | ----------- | ---------- |
+| {packets/sec} | Gauge | Double |
+
+#### Attributes
+
+| Name | Description | Values |
+| ---- | ----------- | ------ |
+| direction | The direction of network throughput. | Str: ``transmitted``, ``received`` |
+| object | The object on the virtual machine or host that is being reported on. | Any Str |
+
 ### vcenter.vm.network.packet.rate
 
 The rate of packets transmitted or received by each vNIC (virtual network interface controller) on the virtual machine.

receiver/vcenterreceiver/internal/metadata/testdata/config.yaml

@@ -81,6 +81,8 @@ all_set:
       enabled: true
     vcenter.vm.network.packet.count:
       enabled: true
+    vcenter.vm.network.packet.drop.rate:
+      enabled: true
     vcenter.vm.network.packet.rate:
       enabled: true
     vcenter.vm.network.throughput:
@@ -194,6 +196,8 @@ none_set:
       enabled: false
     vcenter.vm.network.packet.count:
       enabled: false
+    vcenter.vm.network.packet.drop.rate:
+      enabled: false
     vcenter.vm.network.packet.rate:
       enabled: false
     vcenter.vm.network.throughput: