[cmd/telemetrygen] Support custom metric names via --otlp-metric-name flag (#42089)

<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes #42070

Signed-off-by: odubajDT <ondrej.dubaj@dynatrace.com>

Author: odubajDT

.chloggen/telemetrygen-metric-name.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# 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: cmd/telemetrygen
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Support custom metric names via --otlp-metric-name flag"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [42070]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

cmd/telemetrygen/pkg/metrics/config.go

@@ -41,6 +41,7 @@ func (c *Config) Flags(fs *pflag.FlagSet) {
 	fs.StringVar(&c.HTTPPath, "otlp-http-url-path", c.HTTPPath, "Which URL path to write to")
 
 	fs.IntVar(&c.NumMetrics, "metrics", c.NumMetrics, "Number of metrics to generate in each worker (ignored if duration is provided)")
+	fs.StringVar(&c.MetricName, "otlp-metric-name", c.MetricName, "Metric name of the exported metric")
 
 	fs.StringVar(&c.TraceID, "trace-id", c.TraceID, "TraceID to use as exemplar")
 	fs.StringVar(&c.SpanID, "span-id", c.SpanID, "SpanID to use as exemplar")