fix(core): introduce BootstrapContext for improved server bootstrapping

[alan-agius4]

This commit introduces a number of changes to the server bootstrapping process to make it more robust and less error-prone, especially for concurrent requests.

Previously, the server rendering process relied on a module-level global platform injector. This could lead to issues in server-side rendering environments where multiple requests are processed concurrently, as they could inadvertently share or overwrite the global injector state.

The new approach introduces a BootstrapContext that is passed to the bootstrapApplication function. This context provides a platform reference that is scoped to the individual request, ensuring that each server-side render has an isolated platform injector. This prevents state leakage between concurrent requests and makes the overall process more reliable.

BREAKING CHANGE:
The server-side bootstrapping process has been changed to eliminate the reliance on a global platform injector.

Before:

const bootstrap = () => bootstrapApplication(AppComponent, config);

After:

const bootstrap = (context: BootstrapContext) =>
  bootstrapApplication(AppComponent, config, context);

A schematic is provided to automatically update main.server.ts files to pass the BootstrapContext to the bootstrapApplication call.

In addition, getPlatform() and destroyPlatform() will now return null and be a no-op respectively when running in a server environment.

(cherry picked from commit 8bf80c9)

[josephperrott]

LGTM

Reviewed-for: dev-infra

[AndrewKushnir]

Reviewed-for: public-api

[josephperrott]

LGTM

Reviewed-for: global-approvers

[atscott]

This PR was merged into the repository. The changes were merged into the following branches:

• 18.2.x: ff90477

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