Context in WorkDoneWriter

In addition to the original commit description reproduced below, this CL
updates gopls/go.mod to include a replace directive for x/tools.

CL 409936 eliminated cases where we close over a Context during progress
reporting, except in one instance where it wasn't possible: the
WorkDoneWriter that must implement the io.Writer interface.

Unfortunately it contained a glaring bug that the ctx field was never
set, and the regression test for progress reporting during `go generate`
was disabled due to flakiness (golang/go#49901).

Incidentally, the fundamental problem that CL 409936 addressed may also
fix the flakiness of TestGenerateProgress.

Fix the bug, and re-enable the test.

For golang/go#53781
For golang/go#53823

Change-Id: Ideb99a5525667e45d2e41fcc5078699ba1e0f1a3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/417115
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
(cherry picked from commit 459e2b8)
Reviewed-on: https://go-review.googlesource.com/c/tools/+/417118
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

For golang/go#53823

Change-Id: I25b114561f408322a99a63eb90929f4249127381
Reviewed-on: https://go-review.googlesource.com/c/tools/+/417119
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Peter Weinberger <pjw@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>

Remove the replace directive and update x/tools.

For golang/go#53823

Change-Id: I78681cfdd84834438d20f3815898b18115e3bf8f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/417414
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Nooras Saba‎ <saba@golang.org>