feat(cli): add cloud secrets update command

[shumailxyz]

What this PR does / why we need it:
Adds a new command to update secrets in cloud.

garden cloud secrets update

Which issue(s) this PR fixes:
Fixes #3079

Special notes for your reviewer:

• Added a flag upsert to perform upsert and create missing secrets while updating existing secrets.
• Added a flag update-by-id to update secrets by id.
• As there can be multiple secrets with same name across different env/users, added flags scope-to-env and scope-to-user-id to perform scoped filtering.
• An error is thrown if update is performed by name and after applying all filters, multiple secrets with same name are found.
• Added some unit tests however integration tests are missing for this new command as well as other secrets commands. Would be added separately for all the secrets operations together.

[Orzelius]

I think the documentation should also mention that secrets will be created if they don't exist.

If you want to make the creation of secrets default behavior the command should be upsert not update. If you want to keep it update I think that the creation of new secrets should be behind a flag, something like --upsert.

Although we decided that we won't be testing this e2e with cloud I still think this code should be split into smaller testable parts and unit tests should be written to ensure quality and make future developments easier.

[eysi09]

Great work!

Left a few comments but overall looks good.

[eysi09]

Thanks for addressing the PR comments. Looks good to me!