fix(pd): restore metrics-process emission (#5022)

## Describe your changes
In bumping the various metrics-related crates recently, we overlooked
that the specific metrics emitted by the `metrics-process` crate had
vanished. Bumping the dependency resolves.

Updates the pd metrics tests to check for more patterns. These checks
were failing on the main branch, specifically the `pd_process_*`
patterns.

Also refactors the metrics test to use `rstest`, for more granular
output.

## Issue ticket number and link

Refs #5021

## Testing and review

I've already confirmed that the new tests failed on main, so CI passing
is enough to merge here.

## Checklist before requesting a review

- [x] I have added guiding text to explain how a reviewer should test
these changes.

- [x] If this code contains consensus-breaking changes, I have added the
"consensus-breaking" label. Otherwise, I declare my belief that there
are not consensus-breaking changes, for the following reason:

  > metrics and tests only, does not affect consensus logic

Cargo.toml

@@ -219,6 +219,7 @@ rand_chacha                      = { version = "0.3.1" }
 rand_core                        = { version = "0.6.4" }
 regex                            = { version = "1.8.1" }
 rocksdb                          = { version = "0.21.0" }
+rstest                           = { version = "0.24.0" }
 rustls                           = { version = "0.23.21" }
 serde                            = { version = "1.0.186" }
 serde_json                       = { version = "1.0.96" }

crates/bin/pd/Cargo.toml

@@ -53,7 +53,7 @@ ics23                            = { workspace = true }
 jmt                              = { workspace = true }
 metrics                          = { workspace = true }
 metrics-exporter-prometheus      = { workspace = true }
-metrics-process                  = "2.0.0"
+metrics-process                  = "2.4.0"
 metrics-tracing-context          = { workspace = true }
 metrics-util                     = "0.18.0"
 mime_guess                       = "2"
@@ -127,3 +127,4 @@ assert_cmd = { workspace = true }
 predicates = "2.1"
 prost-reflect = "0.14.3"
 regex = { workspace = true }
+rstest = { workspace = true }