Improve Stardoc docs to cover all public APIs

[ryanulep]

Replaces the old docs/attrs.md (a hand-rolled attributes table covering only the detekt rule) with a comprehensive docs/rules_detekt.md generated by Stardoc, covering all public APIs: detekt,
detekt_test, detekt_create_baseline, detekt_toolchain, rules_detekt_toolchains, and detekt_version.

Changes

• docs/BUILD: Add separate stardoc targets for defs.bzl, toolchain.bzl, toolchains.bzl, and versions.bzl; combine them via a genrule into a single rules_detekt.md output. Remove
  the custom rule_template.vm (no longer needed now that Stardoc's default output format is used).
• docs/generate.sh: Update to move the new generated file.
• docs/attrs.md → docs/rules_detekt.md: Replace old hand-maintained file with the regenerated output.
• detekt/BUILD: Export all public .bzl files so Stardoc can read them.
• detekt/defs.bzl: Add doc strings to detekt, detekt_test, and detekt_create_baseline rules; remove the is_android attr (superseded by enable_type_resolution); polish existing attr
  doc strings.
• detekt/toolchain.bzl, detekt/toolchains.bzl, detekt/versions.bzl: Add/improve doc strings on rules and macros.
• MODULE.bazel: Bump stardoc dev dependency from 0.7.2 → 0.8.1.
• README.md: Update links from docs/attrs.md to docs/rules_detekt.md; fix rules_detekt_dependencies parameter name (detekt_version → detekt).