[dv] The TCK frequence in jtag_if is not configured explicitly for top-level tests

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### Description

At the moment, the frequency comes from `jtag_if.sv` itself. Making this frequency more sensible for GLS meant we needed to add an ifdef (issue #24580). To make this a bit clearer, we should probably:
1. Add something to the top-level test UVM configuration to explicitly set a JTAG frequency.
2. Make the frequency silly if it hasn't been configured, but overridden by something sensible for GLS.
3. "For extra credit": Come up with some way to configure this sensibly for GLS to avoid needing to encode facts about the technology target for Earlgrey into `jtag_if.sv`(!)

Start by reading jtag_if.sv and the top-level test UVM configuration mentioned in the issue, then review issue #24580 for the GLS context. Determine how the TCK frequency is currently selected and what configuration mechanisms are available. Done means top-level tests set it explicitly, an unconfigured value is clearly unsuitable, and GLS can override it without hard-coding Earlgrey technology facts.

Written by the indexing model from the issue text.