Update internal issue templates

[mikealfare]

If both placeholder and value properties are provided, value wins. This means examples cannot be put in the placeholder property in these scenarios. Examples were moved into the description property.

A header is not needed for tasklist fields as it duplicates the field header. They were removed.

More fields were updated to tasklist fields. All tasklist fields use the value property to setup the tasklist structure.

Implementation tasks were moved up to be after Objectives for epics. These fields are more closely related than the previous structure suggested.

It may be easier to see the new versions by looking at the rendered forms:

• epic
• feature

Note that these rendered forms show the description below the input field. This is not how it appears when using the form.

[martynydbt]

thanks for taking them for a spin!