Add Functionality to Ignore Nearly expired RIs with Specified Tags

[mashiike]

This pull request introduces a new feature to exclude expired Reserved Instances (RIs) when specific tags are associated with them, preventing them from being displayed as expired. The motivation behind this feature is to enhance the efficiency of frequent riex executions by excluding RIs that are nearing their expiration date but are already acknowledged.

To achieve this, the functionality leverages the capability of tagging EC2, Elasticache, and RDS instances with Reserved Instances. When a specified tag is present, the associated RIs are considered acknowledged and will be ignored, ensuring they are not included in the display results.

Please review and provide feedback on this pull request. Thank you!

Behavier

For example, RDS RI

in default:

$ go run cmd/riex/main.go 90 --format markdown
| service | name | description | instance_type | count | start_time | end_time | state |
| --- | --- | --- | --- | --- | --- | --- | --- |
| RDS | example-hoge-hoge | aurora-mysql | db.t4g.medium | 1 | 2022-07-01T00:00:00Z | 2023-07-01T00:00:00Z | active |

if add --ignore-tags key1=value1;key2=value2

$ go run cmd/riex/main.go 90 --ignore-tags riex=recognized --format markdown

Currently, it is assumed that the recognized tags are attached manually.