Rework SFDP/BlockDevice to support region overlap

[LDong-Arm]

We have a task #12574 to support parsing multiple SFDP sector maps, to support CYW9P62S1_43012EVB_01. But that is not enough - there's a separate issues that CYW9P62S1_43012EVB_01 has overlaid regions which Mbed OS doesn't support yet.

Explanation:

One of the configurations of CYW9P62S1_43012EVB_01 has the following layout (relative addresses):

• 1st region: Eight 4KB sectors between 0x0000'0000 - 0x0000'7FFF
• 2nd region: One 256KB sector at 0x0000'0000 - 0x0003'FFFF
• 3nd region: A number of 256KB sectors from 0x0004'0000 until the end of the flash

The first two regions overlap. But Mbed OS BlockDevice and SFDP implementations both assume there's no overlap. Some rework is needed.