Di 23858 add monitor apis

[rbajoria26]

📝 Description

This PR adds the monitor APIs used by the ACLP functionality

✔️ How to Test

What are the steps to reproduce the issue or verify the changes?
The changes can be verified by running the following code:

package main

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"os"

	"github.com/linode/linodego"

	"golang.org/x/oauth2"
)

func main() {
	apiKey, ok := os.LookupEnv("LINODE_TOKEN")
	if !ok {
		log.Fatal("Could not find LINODE_TOKEN, please assert it is set.")
	}
	tokenSource := oauth2.StaticTokenSource(&oauth2.Token{AccessToken: apiKey})

	oauth2Client := &http.Client{
		Transport: &oauth2.Transport{
			Source: tokenSource,
		},
	}

	linodeClient := linodego.NewClient(oauth2Client)
	linodeClient.SetDebug(true)

	res, err := linodeClient.ListMonitorServices(context.Background(), nil)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("%v", res)
}

How do I run the relevant unit/integration tests?
Run integration test as follows:

make test-int TEST_ARGS="-run TestMonitorServices_Get_smoke"
make test-int TEST_ARGS="-run TestMonitorDashboards_Get_smoke"
make fixtures TEST_ARGS="-run TestMonitorMetricDefinitions_Get_smoke"
make fixtures TEST_ARGS="-run TestMonitorServicesTokenCreation_Get_smoke"

Run unit test as follows:

make test-unit TEST_ARGS="-run TestListMonitorServices" 
make test-unit TEST_ARGS="-run TestListMonitorDashboards"
make test-unit TEST_ARGS="-run TestListMonitorMetricDefinitionsByType"
make test-unit TEST_ARGS="-run TestCreateMonitorServicesToken"

[yec-akamai]

Thank you for starting contributing to linodego for ACLP! I reviewed the dashboard change and find there are some common issue in the implementation. Can you fix them given the comments as well as in the rest of the PR? i.e. naming, enum, etc.

[yec-akamai]

Can you fix the issue reported by GHA?

[yec-akamai]

Tests passed on my end, nice work!

[rbajoria26]

#722 - created a new PR with updates, the current one got messed up

[yec-akamai]

Close this PR in favor of #722