Log Message:
go124: new package for 1.24.0, from wip.

The latest Go release, version 1.24, arrives six months after Go 1.23.
Most of its changes are in the implementation of the toolchain, runtime,
and libraries. As always, the release maintains the Go 1 promise of
compatibility. We expect almost all Go programs to continue to compile
and run as before.

Go 1.24 now fully supports generic type aliases: a type alias may be
parameterized like a defined type.

Go modules can now track executable dependencies using tool directives
in go.mod.

Several performance improvements to the runtime have decreased CPU
overheads by 2-3% on average across a suite of representative
benchmarks. Results may vary by application. These improvements include
a new builtin map implementation based on Swiss Tables, more efficient
memory allocation of small objects, and a new runtime-internal mutex
implementation.