Autofill onByDefault rollout for new installs

[amddg44]

Task/Issue URL: https://app.asana.com/0/0/1205296228305939/f
Tech Design URL:
CC:

Description:
Adds support for rolling out Autofill as on by default for new installs based on the incremental feature flag onByDefault

Steps to test this PR:
Notes:
This PR branches off of #2032 which added a pixel parameter reporting the "on by default" state.
The rules for enabling Autofill as on by default are:

• User must be a new install (tracking this using userDefaults)
• The subfeature phased rollout feature flag onByDefault must enable the feature for them

1. Clean install the app from develop and confirm that Autofill is off by default
2. Switch to this branch and make the following code changes to test using the correct privacy config
3. Modify the embedded ios-config.json adding the onByDefault subfeature to the autofill json (see https://app.asana.com/0/0/1205590415076770/f)

            "onByDefault": {
                    "state": "enabled",
                    "minSupportedVersion": "7.91.0",
                    "rollout": {
                        "steps": [
                            {
                                "percent": 1.0
                            }
                        ]
                    }
                }

5. In AppURLs change the privacyConfig URL to anything else so the config isn't overwritten from the server e.g. static let privacyConfig = URL(string: "\(staticBase)/trackerblocking/config/v3/ios-config-invalid.json")!
6. Launch the app and confirm that Autofill is still off by default and note that Autofill pixels when accessing the Autofill screen contain the parameter ["default_state": "off"]
7. Modify the ios-config.json steps and add rollout at 100% like so:

           "steps": [
                            {
                                "percent": 1.0
                            },
                            {
                                "percent": 100.0
                            },
                        ]

8. Launch the app again and confirm that the Autofill is still off by default (as reported by the pixel parameter)
9. Toggle the Autofill switch to turn Autofill on, relaunch the app and confirm that Autofill default state is still off (as reported by the pixel parameter)
10. Delete the app and reset ios-config.json to Step 3
11. Launch and confirm that (more than likely, since it's only at 1% rollout) that Autofill default state is off
12. Repeat Step 7
13. Launch the app and confirm that this time Autofill is now on by default

Copy Testing:

• Use of correct apostrophes in new copy, ie ’ rather than '

Orientation Testing:

• Portrait
• Landscape

Device Testing:

• iPhone SE (1st Gen)
• iPhone 8
• iPhone X
• iPhone 14 Pro
• iPad

OS Testing:

• iOS 14
• iOS 15
• iOS 16

Theme Testing:

• Light theme
• Dark theme

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Internal references:

Software Engineering Expectations
Technical Design Template

[graeme]

LGTM. Nice work!