Add `FrameRangedTrait.frameToken` and `FrameRangedTrait.frameTokenRegexp`

[feltech]

What

Add two new string properties to the FrameRanged trait called frameToken and frameTokenRegexp

Why

OpenAssetIO has its own string token substitution standard, which we naively expected all compliant hosts and managers to adopt.

However, the structure of tokenised strings, in particular for representing an image sequence, is deeply entrenched in many host applications. For example they may expect # placeholders (my_sequence.####.exr) or printf style format specifiers (my_sequence.%04d.exr) in a templated path.

There are two cases to consider

1. A host is publishing an image sequence and requests a destination path from the manager as a templated path. In this case the manager must construct a string with a token that the host will understand. I.e. frameToken.
2. A manager receives the location of an image sequence from the host as a templated path, but the asset manager needs to glob the disk to get a list of all the frames as file paths. In this case the manager needs to transform the template to one they can understand. I.e. frameTokenRegexp.

[feltech]

Alternatively, this could be a new trait, since one can imagine things with frame ranges where a frame token is irrelevant, e.g. a video clip.