"tools/gopls" support indexing table-driven subtests in test discovery

[tshihad]

Adds detection and indexing of table-driven subtests (t.Run calls inside range loops) to the test discovery.

[gopherbot]

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[gopherbot]

Message from Gopher Robot:

Patch Set 1:

(1 comment)

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Patch Set 1:

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[gopherbot]

Message from Marcus Thelin:

Patch Set 2:

(1 comment)

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