Lazy/late bundling possible?

## Feature Request

I have multiple projects in production with 100 - 300 lambda functions, they are bundled via `serverless-webpack` and `serverless-esbuild`.

The initial bundling for `serverless-offline` in these projects takes 1-2 hours, which is not really practical from the development perspective.

Is it possible to trigger bundling only when an endpoint is visited, or when a lambda is invoked?

I am a maintainer of `serverless-webpack`, if this requires adaptation from the bundler side I'll see what I can do there.

**Sample Code**

- file: serverless.yml

```yaml
service: my-service

plugins:
- serverless-offline

custom:
serverless-offline:
lazy: true
```

**Expected behavior/code**

A local HTTP server is immediately spun up without the bundling process, individual functions are bundled upon invocation from the local endpoint.

**Additional context/Screenshots**

N/A

Start by tracing how serverless-offline starts its local HTTP server and how endpoint or Lambda invocation currently triggers bundling; the issue does not name implementation files or tests. Done means the server starts without bundling, and each function is bundled when first invoked, including compatibility considerations for serverless-webpack and serverless-esbuild.

Written by the indexing model from the issue text.