Add debug display of Keystore metric info

Output:

```
Metrics information:

  KEYGEN_GENERAL : [
    RSA  ksz=2048 crv=NONE  UNSPECED   rc=   1 attest? N => count=1
    AES  ksz=  -1 crv=NONE  UNSPECED   rc= -67 attest? N => count=1
    AES  ksz=  -1 crv=NONE  UNSPECED   rc=   1 attest? N => count=1
    AES  ksz= 128 crv=NONE  UNSPECED   rc=   1 attest? N => count=1
    AES  ksz= 256 crv=NONE  UNSPECED   rc= -67 attest? N => count=3
    AES  ksz= 256 crv=NONE  UNSPECED   rc=   1 attest? N => count=3
    HMAC ksz= 256 crv=NONE  UNSPECED   rc=   1 attest? N => count=1
  ]
  KEYGEN_AUTH    : [
    auth=UNSPEC log(time)=-1 sec=TEE       => count=11
  ]
  KEYGEN_MODES   : [
    RSA  purpose=----S-- padding=-S---- digest=--2---- blockmode=---- => count=1
    AES  purpose=-----D- padding=-----N digest=------- blockmode=G--- => count=2
    AES  purpose=-----DE padding=-----N digest=------- blockmode=G--- => count=7
    HMAC purpose=---VS-- padding=------ digest=--2---- blockmode=---- => count=1
  ]
  KEYOP_MODES    : [
    ENCRYPT padding=-----N digest=------- blockmode=G--- => count=3
    DECRYPT padding=-----N digest=------- blockmode=G--- => count=1
    SIGN    padding=------ digest=--2---- blockmode=---- => count=1
    SIGN    padding=-S---- digest=--2---- blockmode=---- => count=2
  ]
  KEYOP_GENERAL  : [
    SUCCESS        1 upgraded? N sec=TEE       => count=7
  ]
```

Test: adb shell dumpsys android.security.maintenance (above)
Test: keystore2_client_tests
Test: keystore2_test
Bug: 344987718
Change-Id: I23a79eb564cf4a148414d5fb417f628dce3fc171
diff --git a/keystore2/src/maintenance.rs b/keystore2/src/maintenance.rs
index 7749507..4c895ae 100644
--- a/keystore2/src/maintenance.rs
+++ b/keystore2/src/maintenance.rs
@@ -309,6 +309,12 @@
         }
         writeln!(f)?;
 
+        // Display accumulated metrics.
+        writeln!(f, "Metrics information:")?;
+        writeln!(f)?;
+        write!(f, "{:?}", *crate::metrics_store::METRICS_STORE)?;
+        writeln!(f)?;
+
         // Reminder: any additional information added to the `dump_state()` output needs to be
         // careful not to include confidential information (e.g. key material).