[analyzer] Handle `\l` symbol in string literals in exploded-graph-rewriter

Summary:
Handle `\l` separately because a string literal can be in code like "string\\literal" with the `\l` inside. Also on Windows macros __FILE__ produces specific delimiters `\` and a directory or file may starts with the letter `l`.

Fix:
Use regex for replacing all `\l` (like `,\l`, `}\l`, `[\l`) except `\\l`, because a literal as a rule contains multiple `\` before `\l`.

Differential Revision: https://reviews.llvm.org/D82092