Changes

chore(tekton/v1): add pingcap/tiproxy to Next-Gen build triggers (#3841)

## Overview

This PR expands the build range for the `pingcap/tiproxy` repository to
support Next-Gen branches and tags in the tekton/v1 pipeline system.

## Changes

Added `pingcap/tiproxy` to three Next-Gen trigger configurations:

### 1. Branch Creation Trigger (`git-create-branch-ng.yaml`)
- Triggers on `release-nextgen-*` branch creation (e.g.,
`release-nextgen-1`, `release-nextgen-10`)
- Automatically bumps placeholder versions in README when new Next-Gen
release branches are created

### 2. Branch Push/Build Trigger (`git-push-branch-build-ng.yaml`)
- Triggers builds on pushes to `master` and `release-nextgen-*` branches
- Build configuration:
  - Timeout: 20 minutes
  - Source workspace: 50Gi
  - CPU: 4 cores
  - Memory: 16Gi
- **Profile: `release`** (tiproxy uses `release` profile; other repos
use `next-gen`)

### 3. Tag Creation/Build Trigger (`git-create-tag-build-ng.yaml`)
- Triggers builds on Next-Gen tag creation matching pattern:
`vX.Y.Z-nextgen.YYMMDD.N`
  - Example: `v1.0.0-nextgen.202510.1`, `v8.5.0-nextgen.241022.3`
- Uses same build configuration as branch builds
- **Profile: `release`** (tiproxy uses `release` profile; other repos
use `next-gen`)

## Resource Configuration

The build resources are configured based on:
- Similar-sized components (ticdc, pd) in the Next-Gen pipeline
- Existing tiproxy configuration from tekton/v0
- Conservative allocation suitable for tiproxy's build requirements

## Profile Configuration

A conditional profile overlay has been added to ensure `pingcap/tiproxy`
builds with the `release` profile (consistent with its v0
configuration), while other repositories (ticdc, tidb, tiflash, pd,
cloud-storage-engine) continue to use the `next-gen` profile.

## Testing

- ✅ All modified YAML files validated for syntax correctness
- ✅ Build patterns tested and verified against expected branch/tag
formats
- ✅ Profile assignment logic validated for correct profile selection per
repository
- ✅ CodeQL security analysis passed

## Impact

This change enables the `pingcap/tiproxy` repository to participate in
the Next-Gen build pipeline alongside other core PingCAP components,
supporting the Next-Gen development and release workflow with the
appropriate `release` profile.

Fixes PingCAP-QE/ci#3839

<!-- START COPILOT CODING AGENT SUFFIX -->



<details>

<summary>Original prompt</summary>

> 
> ----
> 
> *This section details on the original issue you should resolve*
> 
> <issue_title>[Next-Gen] expend build range for `pingcap/tiproxy` repo:
support `release-nextgen-*` branches and support `vX.Y.Z-nextgen-*`
tags</issue_title>
> <issue_description></issue_description>
> 
> <agent_instructions>implement it on `tekton/v1`
folder</agent_instructions>
> 
> ## Comments on the Issue (you are @copilot in this section)
> 
> <comments>
> </comments>
> 


</details>

Fixes PingCAP-QE/ci#3839

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 (commit: e25da8b)