5x jump in price from Gold to Platinum is a bit too high. Most of known large deployments target 200-300 hosts. Let's accommodate such users by lowering Platinum tier.

Right now we show only actual size of files on disk which excludes empty blocks of the recently introduced sparced format in #671. This makes impossible to get info about disk size that we just set via `tart set`.

Here is an example of `tart list` output before the change:

```
Source Name                                                                                                            Size State
local  sonoma-base                                                                                                     22   stopped
local  sonoma-vanilla                                                                                                  18   stopped
local  sonoma-xcode                                                                                                    67   stopped
local  ubuntu                                                                                                          1    stopped
oci    ghcr.io/cirruslabs/macos-sonoma-base:latest                                                                     22   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-base@sha256:16c1593bbaf787b20b3c0bc094c5b6baf71c937d22c2e4596da85ac55c92e6cc    22   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-vanilla:14.3                                                                    17   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-vanilla@sha256:23c4e853d48d00a4333346d66a32b2b5aad900cc0dc10e7ecb9dbe67b6f587f4 17   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-xcode:latest                                                                    67   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-xcode@sha256:d0cb8d01424a68b89e0f16f5371bf2152b2c115bd886341a6ba8da42121d1f41   67   stopped
oci    ghcr.io/cirruslabs/ubuntu:22.04                                                                                 1    stopped
oci    ghcr.io/cirruslabs/ubuntu@sha256:037763feb7a15d6077edeb7a097738c34313637d16036764b4c196d28d8b429c               1    stopped
```

And here is the output after the change:

```
Source Name                                                                                                            Disk Size State
local  sonoma-base                                                                                                     50   22   stopped
local  sonoma-vanilla                                                                                                  50   18   stopped
local  sonoma-xcode                                                                                                    90   67   stopped
local  ubuntu                                                                                                          20   1    stopped
oci    ghcr.io/cirruslabs/macos-sonoma-base:latest                                                                     50   22   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-base@sha256:16c1593bbaf787b20b3c0bc094c5b6baf71c937d22c2e4596da85ac55c92e6cc    50   22   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-vanilla:14.3                                                                    50   17   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-vanilla@sha256:23c4e853d48d00a4333346d66a32b2b5aad900cc0dc10e7ecb9dbe67b6f587f4 50   17   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-xcode:latest                                                                    90   67   stopped
oci    ghcr.io/cirruslabs/macos-sonoma-xcode@sha256:d0cb8d01424a68b89e0f16f5371bf2152b2c115bd886341a6ba8da42121d1f41   90   67   stopped
oci    ghcr.io/cirruslabs/ubuntu:22.04                                                                                 20   1    stopped
oci    ghcr.io/cirruslabs/ubuntu@sha256:037763feb7a15d6077edeb7a097738c34313637d16036764b4c196d28d8b429c               20   1    stopped
```

Additionally, `tart get` will print actual size with a 3 decimal point precision which will help to track growth in disk images for our templates.

`tart get` before:

```
CPU Memory Disk Display  State
4   8192   67   1024x768 stopped
```

`tart get` after:

```
CPU Memory Disk Size   Display  State
4   8192   90   67.333 1024x768 stopped
```