Bump lru-cache dependency to ^7.14.1

[MasterOdin]

PR bumps the lru-cache to its latest version (which matches the version string used for mysql2). I had considered lowering the version, but given isaacs/node-lru-cache#257 which was fixed in the latest release, probably not worth allowing older versions.

I also added a test that goes through the cache.get code path as no existing test exercised it to help validate that LRU is (hopefully) working as expected, though cache.get(query) could just always return undefined or whatever.

I also updated the minimum version of this package and what versions of Node are tested against as lru-cache@^7 as a minimal supported node version of 12.

Finally, I ended up changing indentation of some amount of the test file as everything after the should throw error when query contains placeholders but parameters object not passed was indented when it shouldn't have been. Beyond the new test addition, all other changes in that file are just whitespace related.

[MasterOdin]

The dispose method is optional for 7.x at least, and given that the function being passed in was a no-op, decided to remove it. Otherwise, debated on moving the require elsewhere given the need now to do a new call, but decided to leave it as is and just wrap in parentheses as needed.

[sidorares]

the reason require is here instead top of the file to where its used is to avoid cost of loading LRU dependency in case where you have BYO cache library. I'm OK to leave as is but probably splitting into two lines and assigning to a variable could be more readable