fix(tooltips): keep dynamic tooltips from resetting hover delay

[bjnobre]

Cache ALabel tooltip markup and provide it through query-tooltip instead of repeatedly setting GtkWidget's tooltip-markup property. This prevents frequently updating modules from restarting GTK's display-wide tooltip timer.

Keep the active tooltip updated directly so dynamic tooltip contents continue refreshing while the pointer remains stationary.

Problem

Setting tooltip-markup queues a display-wide GTK tooltip query. A
module updating more frequently than GTK's hover delay continually
restarts that delay, preventing its own tooltip—and potentially other
modules' tooltips—from appearing.

Testing

Tested with a custom module updating its displayed text and tooltip every
250 ms, alongside a static control module.

Verified that:

• Both tooltips appear normally.
• The rapidly updating tooltip refreshes while the pointer remains still.
• The rapidly updating module no longer prevents the control tooltip
  from appearing.
• The patched production build compiles and runs with the existing
  Waybar configuration.

Related issues

Related to #4801, #4519, and #4842.

#4812 restored dynamic tooltip synchronization by repeatedly setting
tooltip-markup, but was reverted because doing so resets GTK's hover
state. #4900 subsequently avoided redundant property assignments by
deduplicating identical markup.

That does not cover genuinely dynamic tooltip content: when the value
changes on every update, every assignment is non-redundant and GTK's
display-wide tooltip delay is still continually restarted. This change
provides tooltip content through query-tooltip and updates an already
active tooltip directly, preserving both initial display and live
updates.

Checklist

• Code is formatted with clang-format
• Builds locally (ninja -C build)
• N/A, no user-facing option
  changed
• Tested against the affected module(s)

[Alexays]

Thanks!