main/busybox: upgrade to 1.34.0

The following patches have been manually rebased:

• 0005-udhcpc-set-default-discover-retries-to-5.patch
• 0012-udhcpc-Don-t-background-if-n-is-given.patch

The following patches have been removed since they were applied upstream:

• 001-echo-do-not-assume-that-free-leaves-errno-unmodified.patch
• 0013-use-SOURCE_DATE_EPOCH-for-timestamp-if-available.patch

The following applets were added in this version but not enabled in our busybox configuration: ascii, crc32.