Prepare the 2.16.0.dev6 release.

[benjyw]

No description provided.

[benjyw]

Internal

• go: support building the Go SDK from scratch (#17914)

• upgrade Rust to v1.67.0 (#18109)

• go: merge some tests of the test goal to impove CI times (#18104)

• go: introduce import maps package attribute (#18098)

• go: add basic parsing of vendor/modules.txt files (#18032)

• go: rename generated test main output (#18097)

• use Go 1.19.x in CI (#18099)

• go: pass source file paths to compiler via config file (#18096)

• go: check for out of range indices in asm check helper (#18095)

• Ensure we set the region when deploying to S3. (#18088)

• Migrate remaining frozen_after_init (#18052)

• It's time for more string cleaning (#18046)

• Start phasing out frozen_after_init (#18047)

• Bump to version 0.26.0 of the Toolchain plugin. (#18049)

• Prepare 2.15.0rc2. (#18038)

• Simplify remote store load_bytes API (#18034)

• Move group_by_dir to src/python/pants/util/dirutil.py (#18029)

• Add additional default module mappings (#18031)

• go: missed some obj_dir_path refactors (#18028)

• go: use a Go binary to check for golang assembly files (#17995)

• go: use a directory within sandbox for cgo objects from stdlib packages (#17993)

• Fix wheel reversioning for Linux aarch64. (#18025)

• Speed up multi-python wheel shards. (#18021)