add --postgres-version semver filter flag to 'postgres ls'

[TLINDEN]

The new flag enables operators to filter postgreses by version using semver filters. For instance, these would be valid calls:

# list instances running version 13
$ cloudctl postgres ls --postgres-version 13

# list instances with versions below 15
$ cloudctl postgres ls --postgres-version "< 15"

# list instances with versions between 14 and 16, inclusive
$ cloudctl postgres ls --postgres-version ">= 14, <= 16"

[Gerrit91]

cloud-go v0.35.0 was released.

[TLINDEN]

Rebased.

Also I tested the new flag in the test stage:

$ d postgres ls -o template --template "{{.id}} {{.version}}" --postgres-version ">=16"
6127cdcc-82c9-41f7-8b22-97fe2d318a97 17
6e723e4c-ec75-48d5-a86d-33fb57c9457b 17
732271e0-7a31-4041-a811-9668b3f15ab5 16
ca41bdc7-28c0-4f1d-852d-cca00cf4842d 17
eab3653c-6c95-4ce6-98a6-37ff6574149d 17

$ d postgres ls -o template --template "{{.id}} {{.version}}" --postgres-version "<17"
732271e0-7a31-4041-a811-9668b3f15ab5 16
a3cb9c7b-0c8f-403b-855c-9fbdb71b06c0 12

$ d postgres ls -o template --template "{{.id}} {{.version}}" --postgres-version "12"
a3cb9c7b-0c8f-403b-855c-9fbdb71b06c0 12