chore: bump MCPG (MCP Gateway) from v0.2.17 to v0.2.19 (#26071)

* chore: bump MCPG (MCP Gateway) from v0.2.17 to v0.2.19

Update DefaultMCPGatewayVersion constant and add SHA256 digest pin
for ghcr.io/github/gh-aw-mcpg:v0.2.19 to actions-lock.json.
Recompiled all 187 workflow lock files.

Closes #26068

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* chore: remove stale v0.2.17 MCPG container pin

Remove the old ghcr.io/github/gh-aw-mcpg:v0.2.17 entry from
actions-lock.json to prevent accidental regressions to the older
version. Only the current v0.2.19 pin is retained.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* chore: merge main and recompile workflows with MCPG v0.2.19

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/e2dfd898-cf7c-4470-b1dc-ace3aa543d3b

Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

Author: 3 people

.github/aw/actions-lock.json

@@ -220,11 +220,6 @@
       "digest": "sha256:5411d903f73ee597e6a084971c2adef3eb0bd405910df3ed7bf5e3d6bd58a236",
       "pinned_image": "ghcr.io/github/gh-aw-firewall/squid:0.25.20@sha256:5411d903f73ee597e6a084971c2adef3eb0bd405910df3ed7bf5e3d6bd58a236"
     },
-    "ghcr.io/github/gh-aw-mcpg:v0.2.17": {
-      "image": "ghcr.io/github/gh-aw-mcpg:v0.2.17",
-      "digest": "sha256:a6dec6ec535a11c565d982afa2f98589805ed0598862b9ea9d3c751fc71afae8",
-      "pinned_image": "ghcr.io/github/gh-aw-mcpg:v0.2.17@sha256:a6dec6ec535a11c565d982afa2f98589805ed0598862b9ea9d3c751fc71afae8"
-    },
     "ghcr.io/github/github-mcp-server:v0.32.0": {
       "image": "ghcr.io/github/github-mcp-server:v0.32.0",
       "digest": "sha256:2763823c63bcca718ce53850a1d7fcf2f501ec84028394f1b63ce7e9f4f9be28",