feat: CI - Introduced workflow condition that prevents accidental workflow runs in a forks main branch (#6502)

## Description

The workflow is configured in a way that it will trigger on any changes
in Upstream's (i.e., `Azure/bicep-registry-modules`) `main` branch if
they may have an impact on the module or its validation. However, while
in a fork, the workflow will stop right after initiation thanks to the
condition:
```yml
# Only run if not canceled and not in a fork, unless triggered by a workflow_dispatch event
if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
```
This condition ensures that you don't accidently trigger a large amount
of module workflows when e.g., merging changes from upstream into your
fork. Due to the nature of triggers it's unfortunately not possible to
not trigger them outright.


## Pipeline Reference

<!-- Insert your Pipeline Status Badge below -->

| Pipeline |
| -------- |

[![avm.res.compute.gallery](https://github.com/Azure/bicep-registry-modules/actions/workflows/avm.res.compute.gallery.yml/badge.svg?branch=users%2Falsehr%2FpipelineCond&event=workflow_dispatch)](https://github.com/Azure/bicep-registry-modules/actions/workflows/avm.res.compute.gallery.yml)

## Type of Change

<!-- Use the checkboxes [x] on the options that are relevant. -->

- Azure Verified Module updates:
- [ ] Bugfix containing backwards-compatible bug fixes, and I have NOT
bumped the MAJOR or MINOR version in `version.json`:
- [ ] Feature update backwards compatible feature updates, and I have
bumped the MINOR version in `version.json`.
- [ ] Breaking changes and I have bumped the MAJOR version in
`version.json`.
  - [ ] Update to documentation
- [x] Update to CI Environment or utilities (Non-module affecting
changes)

Author: AlexanderSehr

.github/workflows/avm.ptn.aca-lza.hosting-environment.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.ai-ml.ai-foundry.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.ai-platform.baseline.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.alz.ama.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.alz.empty.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.app-service-lza.hosting-environment.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.app.container-job-toolkit.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.app.iaas-vm-cosmosdb-tier4.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.app.paas-ase-cosmosdb-tier4.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5

.github/workflows/avm.ptn.authorization.pim-role-assignment.yml

@@ -49,6 +49,7 @@ jobs:
   job_initialize_pipeline:
     runs-on: ubuntu-latest
     name: "Initialize pipeline"
+    if: ${{ !cancelled() && !(github.repository != 'Azure/bicep-registry-modules' && github.event_name != 'workflow_dispatch') }}
     steps:
       - name: "Checkout"
         uses: actions/checkout@v5