Case insensitive setting now works for serialized data

[eriktorsner]

Resolves: DELI-1014

In BSR & BSR-PRO v1.4.6, we introduced an early return to skip out of recursive search/replace in serialized data if the target $data is a string (as opposed to object or array) but doesn't contain the search term. However, the early return logic always uses strpos() regardless of what the $case_insensitivesetting is.

In this PR, this is changed so that we select strpos() or stripos() for comparing strings depending on the value of $case_insensitive.

To test

Using version 1.4.6:

1. Add serialized data containing uppercase text to the options table: wp option update --format=json foobar '{"value":"UPPERCASE"}'
2. In BSR, do a dry-run search for "uppercase" in wp_options with Case-Insensitive checked.
3. Note that it reports zero hits.
4. Run the search/replace anyway.
5. Verify that nothing was changed and that foobar still contains "UPPERCASE": wp option get foobar

Using this PR:

7. In BSR, do a dry-run search for "uppercase" in wp_options with Case-Insensitive unchecked.
8. Note that it reports 0 hits.
9. Do another dry-run search for "uppercase" in wp_options, this time with Case-Insensitive checked.
10. Note that it now reports 1 hit.
11. Run the search/replace.
12. Verify that "UPPERCASE" was replaced with the new value: wp option get foobar