feat(topic): Show 'Unlimited' when value is -1

[craicoverflow]

Description

Resolves #488

The -1 value for retention size and retention period means "Unlimited". This adds "Unlimited" to the table alongside the true value of -1.

Verification Steps

Run rhoas kafka topic list:

❯ rhoas kafka topic list
  NAME             PARTITIONS   RETENTION TIME   RETENTION SIZE  
 ---------------- ------------ ---------------- ---------------- 
  strimzi-canary            3   604800000        -1 (Unlimited)  
  topic-1                   1   -1 (Unlimited)   -1 (Unlimited)  
  topic-2                   1   1000000          -1 (Unlimited)

[craicoverflow]

@rkpattnaik780 you might want to have something similar in the UI?