Move all HCI LE Create Connection management into single file

Currently handling of LE Create Connection, LE Create Connection
Cancel, LE Connection Complete and other HCI commands related to LE
connection establishment is in two separate files.
Move all this code into single file.

Bug: 112827989
Test: compilation
Change-Id: Ibc2f6ca2324f4df8a23c2722762d0e5297782b33