[roll] Roll fuchsia [rbe][resultstore] Establish service profile JSON

Establish schema files for existing default RBE/ResultStore
configurations, along with strongly-typed Python dataclass loaders
and subcommand executables.

Designed using a dual-use script architecture:
  1. Python Library: Exposes `Profile` and a strictly pure `load()`
     entrypoint to compiler wrappers and orchestrators, shielding
     them from JSON parsing and on-disk lookup details.
  2. Standalone CLI: Implements a fast, secure, subcommand-based
     interface ('list', 'select', 'active') to manage active
     sticky profiles, avoiding complex Bash logic inside Vars.sh.

- Created build/rbe/profiles and build/resultstore/profiles
  directories with default JSON definitions.
- rbe_profile.py and rs_profile.py:
  - load() resolves, parses, and instantiates the active
    profile in a strictly pure, side-effect-free manner.
  - to_env_dict() serializes profile attributes into standard,
    encapsulated environment variables.
  - Internalized all on-disk directory lookups and sticky name
    lookups behind private-prefixed helper functions.

Original-Original-Bug: 563397434

Original-Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1839410
Original-Original-Revision: 529fa1ecc7acd4b4b4bc645208b8f2c67f1bbe49
GitOrigin-RevId: 6ed853854bcd551436f1e9904d24f9a7c9683b08
Change-Id: I5a0bf82760d922af4b35f4ebc5b551d087ff71aa
Reviewed-on: https://fuchsia-review.googlesource.com/c/integration/+/1883855
Cr-Commit-Position: refs/heads/main@{#205531}