Use TransformRecord to get SPI instead of SpiRecord

IpSecService.applyTunnelModeTransform() currently does not take an
SpiRecord instance, yet implicitly requires that the SpiRecord instance
is still alive based on the stored SpiRecord resourceId in
the TransformRecord's IpSecConfig.

This check is unnecessary, as the SpiRecord has been subsumed into the
TransformRecord, and the kernel resources are kept alive whether or
not the SpiRecord is still held by the user.

This allows users of the IpSecManager API to allocate short-lived SPIs
during the creation of an IpSecTransform, without having to keep track
of both of them (even though the SPI is no longer usable).

The TransformRecord.getSpiRecord() call is already used in
multiple other places in the same method.

Bug: 142072071
Test: New tests added, passing.
Change-Id: I1959f3080946267243564459ff4207647922566e