[Reporting] re-allow multi-page Canvas reports (#255022)

resolves #252838

## Summary

A previous PR - #245330 - added an
incorrect validation on the `locatorParams` parameter, of a maximum of
one entry in the array. Previously there was no limit.

Canvas uses multiple `locatorParams` for multi-page workpads, and so
these ended up failing the validation, and would not generate a report.

This PR changes the limit from 1 to 100.

The validation was added in 9.3.0, so only needs to be backported to the
9.3 branch ...

### To Verify

Create a multi-page Canvas workpad, and generate a PDF for it. Canvas is
not enabled in Kibana by default, anymore, but some instructions to
enable it are here: https://support.elastic.co/knowledge/9f434635

## Release note

Fixes a problem generating a report with multi-page Canvas workpads.

### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [x] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.

Author: pmuellr

x-pack/platform/plugins/private/reporting/server/routes/common/request_handler/validator.test.ts

@@ -365,4 +365,21 @@ describe('validateJobParams', () => {
       ]"
     `);
   });
+
+  it('validates multiple locator params', () => {
+    const validParams = {
+      title: 'Monthly Report',
+      version: '8.0.0',
+      layout: {
+        id: idSchema.Enum.print,
+        dimensions: { width: 800, height: 600 },
+      },
+      browserTimezone: 'UTC',
+      objectType: 'dashboard',
+      forceNow: '2024-01-01T00:00:00',
+      locatorParams: [{ id: 'some-id' }, { version: 'some-version' }],
+    } as unknown as BaseParams;
+
+    expect(() => validateJobParams(validParams)).not.toThrow();
+  });
 });

x-pack/platform/plugins/private/reporting/server/routes/common/request_handler/validator.ts

@@ -95,7 +95,7 @@ const locatorObjectSchema = z.object({
   params: z.record(z.any()).optional(),
 });
 
-const locatorParamsSchema = z.array(locatorObjectSchema).max(1).or(locatorObjectSchema);
+const locatorParamsSchema = z.array(locatorObjectSchema).max(100).or(locatorObjectSchema);
 
 const relativeUrlSchema = z.string().max(4096);
 const relativeUrlsSchema = z.array(relativeUrlSchema).max(100);