all: reopen tree for Go 1.23 development

[joedian]

Current Tree Status: Tree open for Go 1.23 general development (see announcement)

This is a tracking issue for the upcoming task of reopening the tree for Go 1.23 development. (It's created a little early to create room for planning early CLs/branches to land during tree reopening.)

As usual, the tree will initially be open to changes that must land early:

• Bump internal/goversion.Version to 23 and update the go directive in the go.mod files —this should be the very first CL to be submitted as it marks the start of master branch representing Go 1.23 (rather than Go 1.22). (Example CL.)

• Any CLs associated with issues labelled as early-in-cycle.

• Submit CLs that are already approved and marked AutoSubmit, but blocked on wait-release

• Finally, open the tree for all general Go 1.23 changes.

CC @golang/release.

[dmitshur]

Closing as a duplicate of the earlier #64340.