time: LoadLocationFromTZData with slim tzdata uses incorrect zone [1.16 backport]

[gopherbot]

@ianlancetaylor requested issue #44385 to be considered for backport to the next 1.16 minor release.

@gopherbot Please open backport issues.

We mishandle a couple of cases in the time extension strings used by the slim tzdata format. The slim format is likely to appear on more and more systems going forward, and is what we use when people use the time/tzdata package.

[gopherbot]

Change https://golang.org/cl/297230 mentions this issue: [release-branch.go1.16] time: correct unusual extension string cases

[dmitshur]

Approving as a serious issue without a workaround. This backport applies to both 1.16 (this issue) and 1.15 (#44617).

[gopherbot]

Closed by merging 88f91b7 to release-branch.go1.16.