Fix SLO update via dogshell

[aserrallerios]

What does this PR do?

The SLO update is broken. The server side will always return this error no matter the inputs:

ERROR: Invalid payload: 'target' should be number

Also, during SLO updates, name argument is ignored.

This PR fixes both issues.

Description of the Change

We transform the thresholds target string to float, just like in the SLO creation. The DataDog API expects a number in the json body, not a string. We also add the name argument to the parameters of the request.

Alternate Designs

N/A

Possible Drawbacks

None. Probably this never worked and clients are not depending on it.

Verification Process

Empirically on my computer.

Additional Notes

N/A

Release Notes

Fix SLO update via dogshell. This fixes a bug in dogshell that always produced ERROR: Invalid payload: 'target' should be number error during SLO updates, and also takes into account the name argument.

Review checklist (to be filled by reviewers)

• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.

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