[Search Map] Withdraw support for setting default filters

[DieBatzen]

As discussed, support for setting default filters is withdrawn.

Reasons (just for the record):
When calling the search map page, all cache results are already embedded inside the page, no further requests for caches will be done.

In order to apply gclh default filters, there are two options:

1. adapt the embedded results as early as possible, i.e. before further processing starts
   • gclh needs to start as early as possible, which requires to change to @run-at document-start
   • this has the potential to break other functionality, even unnoticed
   • trying to solve this leads to complex and hard to maintain code parts
2. apply the default filters during page load to the filter dialog and perform a filtered search as soon as possible
   • also leads to complex code parts
   • multiple dependencies have to be taken into account
   • can interfere easily with activated option Automatic search for new caches after dragging or zooming
   • trying to prevent this leads to complex and hard to maintain code parts

Moreover, browsers behave slightly different and therefore complex code parts can work perfectly in Chrome but fail in Firefox - or vice versa.
Additionally, either browsers or Tampermonkey behave slightly different in Windows and Linux, which also leads to complications and very high testing effort.

[2Abendsegler]

Further background information on the issue can be found in PR #2739.

[2Abendsegler]

Sieht super aus!