dolphinQt: fix Qt6 deprecation warnings

MemoryWidget: Add Symbols and Notes.

Add option to hide them.
Add box to search.
Add ability to edit data symbols and notes in MemoryViewWidget.

PowerPC: Add RAII handling for breakpoint updates

Fix two bugs that occurred when viewing a memory range starting shortly
before 0xffffffff.

Bug 1: When there was at least one visible memory address at or after
0x0 none of the values would be displayed even when some of the
addresses were valid. This happened because the loop condition in
GetValues immediately returned false since m_address_range.first >
m_address_range.second, causing m_values to be empty. This in turn led
every address to be considered INVALID_MEMORY in UpdateColumns.

Bug 2: When m_address_range.second was equal to 0xffffffff GetValues
would enter an infinite loop. This happened because address would
overflow to 0 after printing the last value in the table, causing the
loop condition address <= m_address_range.second to be true forever.

bbf72e7 made a change where you can pass `false` to certain MemChecks
functions to get them to skip performing an "update" step. It was then
up to the caller to call the Update function later.

This commit changes the implementation so that, instead of the caller
passing in a boolean that controls whether a function calls Update, the
function now returns an object that on destruction will call Update.
Callers that are fine with Update being called right away can skip
storing the object in a variable and thereby call Update immediately,
and callers that want to call Update later can keep the object around.
This new design reduces the risk that someone will forget calling
Update.

Breakpoints: Fix lag when loading multiple memory breakpoints