[helly25]

Add versions.normalize_tuple and versions.normalize_string for collecting interleaved version suffixes and rendering them with configurable separators. Shared-prefix rendering preserves original encounter order: 123+a.b-c.d+e.f-g.h becomes 123#a.b.c.d.e.f.g.h with prefix="#".

AG;DR

• Both functions accept strings or component lists/tuples and share grouping logic. Strings tokenize on ., -, and +; sequences preserve existing component boundaries, spelling, and types.
• Default output groups release, -, then +, preserving encounter order within each group. String rendering accepts a literal separator, None for group markers, or a dict specifying distinct -/+ separators.
• A string prefix merges suffix groups before reordering. A separator dict combined with a shared prefix fails as ambiguous. Release components always render with dots.
• These are mode-independent structural operations, also exposed by with_mode APIs. They do not change parsing or claim standards validation; docs distinguish string tokenization from parsed identifier boundaries and explain empty/malformed input, custom output, and spelling preservation.
• Add regression tests for all discussed examples, sequence/string equivalence, ordering, custom separators and prefixes, invalid inputs, and non-mutation. Keep table columns and inline example comments aligned.
• Validation: all 182 Bazel tests, all 46 Python tests, and focused pre-commit pass. The pushed-head Bazel suite and all six CI checks pass, including Linux, macOS, and Windows.
• Consumer: Cleanup of expression-based version selectors with explicit prerelease control bazel-contrib/toolchains_llvm#911 now replaces _version_string with normalize_string and temporarily pins this PR's source. Its 43 Bzlmod tests, 41 WORKSPACE tests, Trunk checks, and three integration-module graphs pass. Merge this bzl change and publish 0.8.0 before removing the consumer overrides. The bzl release remains on hold.