[otelcol] Tell all loggers to encode timestamps in ISO8601. (#10543)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
OTel collector log messages in Windows are currently displayed in
scientific notation, e.g.:
```
1.7194132367192364e+09  error   scraperhelper/scrapercontroller.go:197  Error scraping metrics  …
```
This fix will cause the log messages to use ISO8601 timestamps instead.

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Manual testing.

<!--Describe the documentation added.-->
#### Documentation
The previous behavior was undocumented, so no documentation changes
needed.

<!--Please delete paragraphs that you did not use before submitting.-->

---------

Co-authored-by: Daniel Jaglowski <[email protected]>

Author: igorpeshansky

.chloggen/igorpeshansky-windows-logger-timestamps.yaml

@@ -0,0 +1,28 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: otelcol
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Change all logged timestamps to ISO8601.
+
+# One or more tracking issues or pull requests related to the change
+issues: [10543]
+
+# (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: |-
+  This makes log timestamps human-readable (as opposed to epoch seconds in
+  scientific notation), but may break users trying to parse logged lines in the
+  old format.
+
+# 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: [user]

otelcol/collector_windows.go

@@ -225,6 +225,7 @@ func withWindowsCore(elog *eventlog.Log, serviceConfig **service.Config) func(za
 		// Use the Windows Event Log
 		encoderConfig := zap.NewProductionEncoderConfig()
 		encoderConfig.LineEnding = "\r\n"
+		encoderConfig.EncodeTime = zapcore.ISO8601TimeEncoder
 		return windowsEventLogCore{core, elog, zapcore.NewConsoleEncoder(encoderConfig)}
 	}
 }

service/telemetry/logger.go

@@ -13,11 +13,13 @@ import (
 // newLogger creates a Logger and a LoggerProvider from Config.
 func newLogger(set Settings, cfg Config) (*zap.Logger, log.LoggerProvider, error) {
 	// Copied from NewProductionConfig.
+	ec := zap.NewProductionEncoderConfig()
+	ec.EncodeTime = zapcore.ISO8601TimeEncoder
 	zapCfg := &zap.Config{
 		Level:             zap.NewAtomicLevelAt(cfg.Logs.Level),
 		Development:       cfg.Logs.Development,
 		Encoding:          cfg.Logs.Encoding,
-		EncoderConfig:     zap.NewProductionEncoderConfig(),
+		EncoderConfig:     ec,
 		OutputPaths:       cfg.Logs.OutputPaths,
 		ErrorOutputPaths:  cfg.Logs.ErrorOutputPaths,
 		DisableCaller:     cfg.Logs.DisableCaller,