Add complete option to LineMatcher methods

[SemTiOne]

Closes #6820

Adds a complete option to LineMatcher.fnmatch_lines and LineMatcher.re_match_lines. The assertion fails on unasserted output lines.

Prior art: blueyed#257 explored this first. This converges on the per-call flag while reporting all unasserted lines at the end instead of failing at the first gap, so trailing leftovers are caught too.

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[RonnyPfannschmidt]

the original issue noted that this maybe better served as option

as part of the matchers experiments i have been considering that rather than adding bools to this method

we should have a matcher to specify the behaviour

this should be shelved for a design decission

[SemTiOne]

Thanks, that makes sense. Is there a sketch of the matcher API I could target? Since this is default-off, a later matcher API could subsume it without breaking existing callers. Acceptable as an interim step, or shelve until the design decision lands?

[RonnyPfannschmidt]

for now shelfe - i may need a bit longer to get back to making a POC of matchers - currently its a internal design document only