Properly handle side-effects in matchers

[BenWeber42]

Capturer is a matcher with side-effects. The side-effects are applied when a Capturer submatcher matches. However, they should only be applied when the whole matcher matches.

Example:

OneOf(
  FixedList(
    Capture(_).append("wrong"),
    name("123) # this will always fail
  ),
  Capture(_).append("wrong")
)

The first Capture matcher is always executed, but the first option will fail. However, the state will already be modified.
The second Capture will succeed, but it will operate on the incorrectly modified state from the first Capture.

Since matchers are allowed to have side-effect, such side-effects should be properly supported.

[BenWeber42]

With this we can have a safer implementation of the Capture matcher as well. In particular, throw if a single variable is captured multiple times (

dusk/dusk/match.py

Line 135 in 823ae00

# TODO: throw if value already exists?

) as well as match first and only capture after the sub matcher succeeded (

dusk/dusk/match.py

Line 140 in 823ae00

# FIXME: figure out correct order of capturing/matching

)