Fix off-by-1 error in memap's symbol-contained-in-memory-bank check, clean up some linker script stuff

[multiplemonomials]

Summary of changes

I noticed that for targets that had stack fill up until the end of a memory bank, the new memap version was doing some weird stuff:

• It would print a warning about the symbol going outside of the memory bank,
• And, that warning would have the wrong name, it would call out a previous symbol name rather than saying it was *fill* that did it

Turns out there was an off by 1 error in the check for whether a symbol went outside a memory bank, and an issue with the regex that detected the names of input sections.

Impact of changes

Migration actions required

Documentation

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Pull request type

[X] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[] Covered by existing mbed-os tests (Greentea or Unittest)
[X] Tests / results supplied as part of this PR

Verified that we aren't seeing the memap warning after this issue.

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