oeqa/selftest: Adds test case for sdk-update eSDK

oeqa/selftest: Adds test case for sdk-update eSDK

1. Test case adds perl recipe before build eSDK.
2. After this added recipe, the script verifies the update:

    ${SDK_DEPLOY}/${TOOLCHAINEXT_OUTPUTNAME}.sh
    oe-publish-sdk [esdk] [path-to-http]
    CORE_IMAGE_EXTRA_INSTALL = "perl"
    bitbake -c populate-sdk-ext [some-image]
    devtool sdk-update

This should fix [YOCTO #9369]

Signed-off-by: Francisco Pedraza <francisco.j.pedraza.gonzalez@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>