rpk cluster config get: avoid scientific notation

The scientific notation was from json unmarshal rules. We now convert to
int64 directly.

Note that edit, import, and export all handle this already.

We remove the one impossible branch in export, since we know we cannot
have an `int` in the config map, and we remove the hack in the test that
converted from scientific notation.

Closes redpanda-data#6070.

src/go/rpk/pkg/cli/cmd/cluster/config/export.go

@@ -99,8 +99,6 @@ func exportConfig(
 		} else {
 			scalarVal := ""
 			switch x := curValue.(type) {
-			case int:
-				scalarVal = strconv.Itoa(x)
 			case float64:
 				scalarVal = strconv.FormatFloat(x, 'f', -1, 64)
 			case string:

src/go/rpk/pkg/cli/cmd/cluster/config/get.go

@@ -46,6 +46,13 @@ output, use the 'edit' and 'export' commands respectively.`,
 			if !exists {
 				out.Die("Property '%s' not found", key)
 			} else {
+				// currentConfig is the result of json.Unmarshal into a
+				// map[string]interface{}. Due to json rules, all numbers
+				// are float64. We do not want to print floats, especially
+				// for large numbers.
+				if f64, ok := val.(float64); ok {
+					val = int64(f64)
+				}
 				// Intentionally bare output, so that the output can be readily
 				// consumed in a script.
 				bytes, err := yaml.Marshal(val)

tests/rptest/tests/cluster_config_test.py

@@ -939,11 +939,6 @@ def yamlize(input) -> str:
 
             expect_cli_readback = yamlize(e.yamlval)
 
-            # Hack around scientific notation for large int values.
-            # This may be an RPK bug?
-            if cli_readback.find("e+") != -1:
-                cli_readback = str(int(float(cli_readback)))
-
             self.logger.info(
                 f"CLI readback '{cli_readback}' expect '{expect_cli_readback}'"
             )