In the marker schema, support label templates with conditional behavior depending on whether a field is present

[mstange]

We have custom code for the FileIO marker's tableLabel:

profiler/src/profile-logic/marker-schema.js

Lines 307 to 315 in c195710

	if (data.source) {
	description = `(${data.source}) `;
	}
	description += data.operation;
	if (data.filename) {
	description = data.operation
	? `${description} — ${data.filename}`
	: data.filename;
	}

Mostly what's happening is that some fields are optional, and those fields shouldn't be surrounded by brackets or separated by spaces or dashes if they're not present.

It would be nice if we could achieve the same result with some extensions to the label template syntax.

A similar request was made in the past by @fqueze, when he wanted to share the same schema for these two markers, to reduce code duplication at the schema declaration: https://share.firefox.dev/4fWgc0B

┆Issue is synchronized with this Jira Task

[mstange]

We could take inspiration from the Jujutsu template syntax. It has functions surround and separate which ignore empty inputs.

For example, the FileIO tableLabel could be {separate(' — ', separate(' ', surround('(', ')', marker.data.source), marker.data.operation), marker.data.filename)}