[source-google-analytics-data-api] Add option to merge multi-property data into single streams instead of creating separate tables per property

## Problem

When the GA4 source connector (`source-google-analytics-data-api`) is configured with multiple property IDs, it creates **separate streams (and therefore separate destination tables) for each property beyond the first**:

- First property → `` (e.g., `daily_active_users`)
- Additional properties → `Property` (e.g., `daily_active_usersPropertyXXXXXXXXX`)

This is implemented in the manifest at the stream naming logic:

```yaml
# NOTE: Yes, this is weird, but it exists solely for backward-compatibility.
# When the config contains multiple property IDs, it keeps the
# first stream as , and names each additional stream
# Property.
- type: ComponentMappingDefinition
field_path: ["**", "name"]
value: "{{ components_values['name'] + 'Property' + components_values['source_config_1'][1] if components_values['source_config_1'][0] > 0 else components_values['name'] }}"
```

([manifest.yaml, line 925-931](https://github.com/airbytehq/airbyte/blob/master/airbyte-integrations/connectors/source-google-analytics-data-api/manifest.yaml#L925-L931))

### Core issue

While each record already contains a `property_id` column and `property_id` is part of the primary key, the stream-level splitting means data from different properties lands in **different destination tables**. This introduces a dynamic schema problem:

- Adding or removing property IDs changes the set of streams/tables in the catalog
- Downstream queries, dashboards, and BI tools break because they expect a fixed set of tables
- Users get N× the expected number of tables, all with identical schemas but different names
- The `property_id` column already exists and could serve to distinguish data within a single table, making the split unnecessary

### Current workarounds

Users must either:
1. Create separate Airbyte sources per property ID
2. Manually create SQL views or dbt models to `UNION ALL` the per-property tables back together
3. Use only a single property ID per connection

All of these add operational complexity.

## Proposed Solution

Add a configuration option (e.g., `merge_property_streams: true/false`) that, when enabled:

1. **Emits a single stream per report** regardless of how many property IDs are configured (e.g., just `daily_active_users`, not `daily_active_usersPropertyXXX`)
2. **Includes `property_id` as a column** in every record (already the case today)
3. **Keeps `property_id` as part of the primary key** (already the case today)

The default should preserve the current behavior (`false`) for backward compatibility. The code change would be localized to the stream naming `ComponentMappingDefinition` in the manifest.

## Impact

This would allow users with multiple GA4 properties to get a single, stable table per report in their destination — which is the expected behavior for most analytics workflows.

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[Devin session](https://app.devin.ai/sessions/09dd5de762944f4c8b1b645257cdc02b)

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**Internal Tracking:** https://github.com/airbytehq/oncall/issues/11369