aws-type: changing preferred instance type to m6i, instead of m5/m4

[mtulio]

That changes is part of WIP lab to validate gp3 volume type in newest instance types (m5 and m6i).

AWS recently launched the instance m6i, new generation of Nitro instance for general purpose (m5).

ATM the instance is available in a few regions, but the fallback will work well for m5 that was tested on PR openshift#5162 (1)

I successful launched the m6i, but some changes may need to be done. I will keep the list:

• change bootstrap instance type (how to use m5 as fallback?)
• update the docs?
• e2e tests?

1. Regions that has m6i available

Out[17]: 
            region  count(m6i.large)  count(m5.large)  count(m6i<>m5)
0       af-south-1                 0                3              -3
1        ap-east-1                 0                3              -3
2   ap-northeast-1                 2                3              -1
3   ap-northeast-2                 0                4              -4
4       ap-south-1                 0                3              -3
5   ap-southeast-1                 2                3              -1
6   ap-southeast-2                 0                3              -3
7     ca-central-1                 0                3              -3
8     eu-central-1                 2                3              -1
9       eu-north-1                 0                3              -3
10      eu-south-1                 0                3              -3
11       eu-west-1                 3                3               0
12       eu-west-2                 0                3              -3
13       eu-west-3                 0                3              -3
14      me-south-1                 0                3              -3
15       sa-east-1                 0                3              -3
16       us-east-1                 5                5               0
17       us-east-2                 3                3               0
18       us-west-1                 2                2               0
19       us-west-2                 4                4               0

2. Successful provisioning changing preferred instance.