Support Go 1.27 by upgrading golang.org/x/tools to v0.48.0

[moisesvega]

Why

Go 1.27's compiler emits export data version 4, which the pinned golang.org/x/tools v0.36.0 cannot decode. mockgen's package mode imports type information through x/tools, so generating mocks on Go 1.27 (currently rc2) fails with:

internal error in importing "..." (cannot decode "...", export data version 4 is greater than maximum supported version 2); please report an issue

What

• Upgrade golang.org/x/tools v0.36.0 → v0.48.0 (with x/mod v0.38.0, x/sync v0.22.0).
• Bump the module's minimum Go version 1.23 → 1.25. This is unavoidable: I bisected x/tools releases and v0.44.0 is the first that decodes the new export-data format, and it already requires Go 1.25 — there is no upgrade path that keeps 1.24 support.
• Re-tidy the generics and typed test sub-modules, which replace the main module.
• CI: test matrix [1.24.x, 1.25.x] → [1.25.x, 1.26.x, 1.27.0-rc.2] (1.24.x can no longer build the module; the rc entry guards against future export-data bumps); release workflow 1.23.x → 1.25.x.

The bazel module is unaffected — it pins the published go.uber.org/mock v0.6.0 with its own SDK, so it picks up Go 1.27 support with the next release.

Test Plan

Full test suite passes on both go1.27rc2 and go1.26.4 (all packages, including the tools, generics, and typed sub-modules), go vet ./... is clean, and both ci/test.sh and ci/check_panic_handling.sh pass locally with go1.27rc2.