Support underscores for block names

[michael-follmann]

Describe the current behavior

However, we noticed in the Prefect Cloud UI that different validation rules are applied for different resource names.

For example:

• For blocks the following rule is applied: Name must only contain lowercase letters, numbers, and dashes
• Variables use this rule: Name may only contain letters, numbers, dashes, and underscores and may not begin or end with a dash or underscore

Describe the proposed behavior

Could you please support underscores for block names to give us more flexibility with the naming and make the naming rules more consistent?

Example Use

To avoid naming conflicts between teams within the same workspace, we strive for a naming convention across various Prefect resources (e.g. flows, deployments, blocks, variables, work pools,...).

Additional context

No response

[naaa760]

@michael-follmann please check it out!

[zzstoatzz]

see https://github.com/PrefectHQ/prefect/pull/19592#issuecomment-3607649246