[receiver/hostmetrics] Add new process metrics (open-telemetry#12972)

Add the following process metrics:
- `process.context_switches`
- `process.open_file_descriptors`

Co-authored-by: Evan Bradley <[email protected]>

.chloggen/hostmetricsreceiver-new-metrics.yaml

@@ -0,0 +1,16 @@
+# 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: hostmetricsreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add new process metrics
+
+# One or more tracking issues related to the change
+issues: [12482]
+
+# (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 `process.context_switches` and `process.open_file_descriptors` as process metrics. They are disabled by default.

receiver/hostmetricsreceiver/internal/scraper/processscraper/documentation.md

@@ -8,11 +8,13 @@ These are the metrics available for this scraper.
 
 | Name | Description | Unit | Type | Attributes |
 | ---- | ----------- | ---- | ---- | ---------- |
+| process.context_switches | Number of times the process has been context switched. | {count} | Sum(Int) | <ul> <li>context_switch_type</li> </ul> |
 | **process.cpu.time** | Total CPU seconds broken down by different states. | s | Sum(Double) | <ul> <li>state</li> </ul> |
 | **process.disk.io** | Disk bytes transferred. | By | Sum(Int) | <ul> <li>direction</li> </ul> |
-| **process.memory.physical_usage** | The amount of physical memory in use. | By | Sum(Int) | <ul> </ul> |
+| **process.memory.physical_usage** | The amount of physical memory in use | By | Sum(Int) | <ul> </ul> |
 | **process.memory.virtual_usage** | Virtual memory size. | By | Sum(Int) | <ul> </ul> |
-| process.paging.faults | Number of page faults the process has made. This metric is only available on Linux. | {faults} | Sum(Int) | <ul> <li>type</li> </ul> |
+| process.open_file_descriptors | Number of file descriptors in use by the process. | {count} | Sum(Int) | <ul> </ul> |
+| process.paging.faults | Number of page faults the process has made. This metric is only available on Linux. | {faults} | Sum(Int) | <ul> <li>paging_fault_type</li> </ul> |
 | process.threads | Process threads count. | {threads} | Sum(Int) | <ul> </ul> |
 
 **Highlighted metrics** are emitted by default. Other metrics are optional and not emitted by default.
@@ -40,6 +42,7 @@ metrics:
 
 | Name | Description | Values |
 | ---- | ----------- | ------ |
+| context_switch_type (type) | Type of context switched. | involuntary, voluntary |
 | direction | Direction of flow of bytes (read or write). | read, write |
+| paging_fault_type (type) | Type of memory paging fault. | major, minor |
 | state | Breakdown of CPU usage by type. | system, user, wait |
-| type | Type of memory paging fault. | major, minor |