Incorrect LIKE result when pattern contains \\ double backslash

[findepi]

Incorrect LIKE result when pattern contains \\ two backslashes

\ in LIKE pattern is an escape character (but see #13291)

query B
SELECT '%' LIKE '\%'
----
true

query B
SELECT 'a' LIKE '\%'
----
false

so this should return true

# should be true
query B
SELECT '\a' LIKE '\\%'
----
false

notes

• testing this in CLI is currently impossible due to Incorrect backslash treatment in string literals in DataFusion CLI #13286
• the bug was originally posted in a comment: Test LIKE with implicit \ escape #13288 (comment)
• maybe we should rethinking implicit escape, but that's likely orthogonal Support LIKE pattern without any escape character #13291

[findepi]

Should be fixed by apache/arrow-rs#6703

[findepi]

This is now fixed, but let's add '\a' LIKE '\\%' to the regression tests: #14501