Add Leo skills metrics

[DJAndries]

Add the following weekly metrics:

If you used Leo skills in the past week, how many conversations did you engage in the past week?
Brave.AIChat.SkillsWeeklySessions

1. 1-5
2. 6-10
3. 11-20
4. 21+

If you used Leo skills in the past week, what was the most used entry point?
Brave.AIChat.SkillsEntryPoint

1. Implicit (typed naturally)
2. Explicit (clicked from menu)

If you used Leo skills in the past week, what was the average amount of skill prompts per chat?
Brave.AIChat.SkillAvgPrompts

1. 1-3
2. 4-10
3. 11-20
4. 21+

If you used Leo in the past week, what percentage of chats this week used skills?
Brave.AIChat.PercentChatsWithSkill

0. 0%
1. Greater than 0%, less than or equal to 25%
2. Greater than 25%, less than or equal to 50%
3. Greater than 50%, less than or equal to 75%
4. Greater than 75%

If you used Leo in the past month, how many skilled prompts were made?
Brave.AIChat.SkillMonthlyPrompts

1. 1
2. 2-3
3. 4-10
4. 11+

If you used Leo skills in the past week, what was the average session duration?
Brave.AIChat.SessionDurationWithSkill

0. Less than a minute
1. Up to 3 minutes
2. 4-10 minutes
3. 11-20 minutes
4. 21+ minutes

If you used Leo skills, when was the last usage of a skill?
Brave.AIChat.SkillsLastEngagementTime

1. Within the last 6 days
2. 7–13 days ago
3. 14–20 days ago
4. 21–27 days ago
5. 28–59 days ago
6. 60 days ago or more

If you have at least one Leo skill, how many skills do you have?
Brave.AIChat.SkillsCount

1. 1-3
2. 4-10
3. 11-20
4. 21+

If you used Leo skills in the past week, how many unique skills did you use?
Brave.AIChat.SkillsUsed

1. 1-3
2. 4-10
3. 11-20
4. 21+

cc @mattmcalister