Use enumer to generate String() methods for most enums (#25705)

We have many hand-written String() methods (and similar) for enums.
These require more maintenance and are more error-prone than using
automatically generated methods. In addition, the auto-generated
versions can be more efficient.

Here, we switch to using https://github.com/loggerhead/enumer, itself
a fork of https://github.com/diegostamigni/enumer, no longer maintained,
and a fork of the mostly standard tool
https://pkg.go.dev/golang.org/x/tools/cmd/stringer.
We use this fork of enumer for Go 1.20+ compatibility and because
we require the `-transform` flag to be able to generate
constants that match our current code base.

Some enums were not targeted for this change:

builtin/logical/pki/tidystatusstate_enumer.go

@@ -0,0 +1,53 @@
+// Code generated by "enumer -type=tidyStatusState -trimprefix=tidyStatus"; DO NOT EDIT.
+
+package pki
+
+import (
+	"fmt"
+)
+
+const _tidyStatusStateName = "InactiveStartedFinishedErrorCancellingCancelled"
+
+var _tidyStatusStateIndex = [...]uint8{0, 8, 15, 23, 28, 38, 47}
+
+func (i tidyStatusState) String() string {
+	if i < 0 || i >= tidyStatusState(len(_tidyStatusStateIndex)-1) {
+		return fmt.Sprintf("tidyStatusState(%d)", i)
+	}
+	return _tidyStatusStateName[_tidyStatusStateIndex[i]:_tidyStatusStateIndex[i+1]]
+}
+
+var _tidyStatusStateValues = []tidyStatusState{0, 1, 2, 3, 4, 5}
+
+var _tidyStatusStateNameToValueMap = map[string]tidyStatusState{
+	_tidyStatusStateName[0:8]:   0,
+	_tidyStatusStateName[8:15]:  1,
+	_tidyStatusStateName[15:23]: 2,
+	_tidyStatusStateName[23:28]: 3,
+	_tidyStatusStateName[28:38]: 4,
+	_tidyStatusStateName[38:47]: 5,
+}
+
+// tidyStatusStateString retrieves an enum value from the enum constants string name.
+// Throws an error if the param is not part of the enum.
+func tidyStatusStateString(s string) (tidyStatusState, error) {
+	if val, ok := _tidyStatusStateNameToValueMap[s]; ok {
+		return val, nil
+	}
+	return 0, fmt.Errorf("%s does not belong to tidyStatusState values", s)
+}
+
+// tidyStatusStateValues returns all values of the enum
+func tidyStatusStateValues() []tidyStatusState {
+	return _tidyStatusStateValues
+}
+
+// IsAtidyStatusState returns "true" if the value is listed in the enum definition. "false" otherwise
+func (i tidyStatusState) IsAtidyStatusState() bool {
+	for _, v := range _tidyStatusStateValues {
+		if i == v {
+			return true
+		}
+	}
+	return false
+}