internal/lsp: determine diagnostics to show per-file, not per-package
internal/lsp: determine diagnostics to show per-file, not per-package

Previously, if any one file in a package had a parse error, we would not
send type errors for any of the other files. Now we make this decision
per-file, so that, even if a file has parse errors, type errors in the
other files will be shown.

Fixes golang/go#32596

Change-Id: I086c04f0ec37cd1b33845153328faf368232d834
Reviewed-on: https://go-review.googlesource.com/c/tools/+/182466
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Cottrell <52376736e5e84615ec49f9c1843b8acc178b1d8d@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools