Reduce duplication in nextest/ODBC CI target lists and arm64 test templates

[Copilot]

The Alpine and deb/rhel distro target lists in validation-stages.yml were written out twice each — once for x64 stages (matrix format) and once for arm64 stages (targets-list format). Adding or removing a distro required editing multiple places and invited drift.

Changes

Unified parameter format for x64 matrix templates

• test-matrix-template.yml and test-matrix-template-alpine.yml: replaced matrix: {} parameter with targets: [] (matching the existing arm64 template contract). The ADO strategy.matrix is generated internally via ${{ each target in parameters.targets }}, so runtime variables $(container) and $(entry) in script steps are unchanged.

Single source of truth for target lists (validation-stages.yml)

YAML anchors replace the four inline duplicate lists:

# Defined once in Test_alpine:
targets: &alpine_targets
  - name: Alpine3_18
    container: ghcr.io/microsoft/mssql-rs/import/alpine:3.18
    entry: alpine.sh
  ...

# Aliased in Test_alpine_arm64:
targets: *alpine_targets

Same pattern for &deb_rhel_targets / *deb_rhel_targets across Test_amd64 and Test_arm64. Adding or removing a distro is now a single-location edit.

Sync comments on arm64 templates

Added comments to both test-matrix-template-arm64.yml and test-matrix-template-alpine_arm64.yml noting that the shared-mode and per-job-mode steps: blocks are structurally identical — differing only in variable sourcing ($(…) runtime vs ${{ target.* }} compile-time) — and must be kept in sync. ADO template constraints prevent further factoring.

• Fixes Reduce duplication in ODBC/nextest CI target lists and arm64 test template #138

[Copilot]

Pull request overview

This PR reduces CI matrix duplication by standardizing target parameters and documenting synchronized ARM64 paths.

Changes:

• Converts x64 matrix templates to target lists.
• Reuses distro lists via YAML anchors.
• Documents duplicated ARM64 step blocks.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
.pipeline/templates/validation-stages.yml	Shares distro target lists between architectures.
.pipeline/templates/test-matrix-template.yml	Generates the amd64 matrix from targets.
.pipeline/templates/test-matrix-template-arm64.yml	Documents synchronized ARM64 paths.
.pipeline/templates/test-matrix-template-alpine.yml	Generates the Alpine matrix from targets.
.pipeline/templates/test-matrix-template-alpine_arm64.yml	Documents synchronized Alpine ARM64 paths.