time: output does not respect comma as millisecond separator [1.17 backport]

[gopherbot]

@cherrymui requested issue #48037 to be considered for backport to the next 1.17 minor release.

@gopherbot please consider backporting it into 1.17. Thanks.

[cagedmantis]

This issue has been approved as it is a major issue without any viable workarounds.

[gopherbot]

Change https://golang.org/cl/350149 mentions this issue: [release-branch.go1.17] time: propagate "," separator for fractional seconds into Format

[gopherbot]

Closed by merging e79c297 to release-branch.go1.17.