[WIP] repl: don't use lineParser for Recoverable errors

[lance]

Removing the REPL's lineParser.shouldFail checks resolves the issue below and does not cause any regressions in the test suite. It appears that when editorMode was backported to the 6.x branch, the LineParser failure checks were not removed.

Fixes: #15704
Ref: 39d9afe
Ref: 4875aa2

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

repl

[Fishrock123]

@lance Is this a backport? What was the original commit / PR?

cc @MylesBorins

[lance]

@Fishrock123 hmm - well, it's a partial backport of 39d9afe but incomplete. I think I need to mark this as a WIP for now.

[lance]

Closing this PR to do a real backport PR as outlined in the backporting-to-release-lines.md