gopls/internal/migrate.sh: a script to migrate internal/lsp to gopls/
gopls/internal/migrate.sh: a script to migrate internal/lsp to gopls/

Add a script that does the migration of the internal/lsp directory to
gopls/internal/lsp. This is done in a separate CL so that in-progress
CLs can rebase on top of *this CL*, run this script, and then rebase to
tip.

For golang/go#54509

Change-Id: I6f529c1e4ba29b4d88dc26278d54a055f1ef212e
Reviewed-on: https://go-review.googlesource.com/c/tools/+/426795
gopls-CI: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Alan Donovan <7069e9552f9d110b0a0f326b96f22f63fb99dfc1@google.com>
Run-TryBot: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>

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