Migrate widevine all prefs from profile to local_state

[simonhong]

After widevine cdm is installed, any user(profile) can use cdm library.
so, it doesn't make sense to ask again whenever new profile is created.

Reproduce step:

1. Launch browser with clean profile
2. Install widevine cdm (via https://shaka-player-demo.appspot.com/demo/#audiolang=en-US;textlang=en-US;uilang=en-US;asset=https://storage.googleapis.com/shaka-demo-assets/sintel-widevine/dash.mpd;panel=HOME;build=uncompiled)
3. Create new profile
4. Load again(https://shaka-player-demo.appspot.com/demo/#audiolang=en-US;textlang=en-US;uilang=en-US;asset=https://storage.googleapis.com/shaka-demo-assets/sintel-widevine/dash.mpd;panel=HOME;build=uncompiled)
5. Check widevine prompt is displayed again

Result: prompt is displayed again. (Regardless of allow/deny, user can play contents)
Expected: prompt should not be displayed.

[simonhong]

kWidevineOptedIn, kAskWidevineInstall and kWidevineInstalledVersion

[btlechowski]

Verification passed on

Brave	1.3.85 Chromium: 79.0.3945.88 (Official Build) beta (64-bit)
Revision	c2a58a36b9411c80829b4b154bfcab97e581f1f3-refs/branch-heads/3945@{#954}
OS	Ubuntu 18.04 LTS

Verified test plan from the description. The widevine prompt is not shown again.

Verification passed on

Brave	1.3.87 Chromium: 79.0.3945.117 (Official Build) beta (64-bit)
Revision	04f0a055010adab4484f7497fbfdbf312c307f1d-refs/branch-heads/3945@{#1019}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified test plan from the description

Verification PASSED on macOS 10.15.2 x64 using the following build:

Brave	1.3.91 Chromium: 79.0.3945.117 (Official Build) beta (64-bit)
Revision	04f0a055010adab4484f7497fbfdbf312c307f1d-refs/branch-heads/3945@{#1019}
OS	macOS Version 10.15.2 (Build 19C57)

• Verified using the cases outlined under Migrate widevine all prefs from profile to local_state #6747 (comment)
• Also went through the same STR but used https://www.netflix.com & https://www.disneyplus.com