Measure and report basic terminal performance marks

[Tyriar]

Part of #185393

@jrieken changes to timer service:

• Terminal reconnection typically happens after restored, this seems preferable to delaying LifecyclePhase.Restored. I also looked into including terminal stats in IStartupMetrics.timers but that's a layer breaker.

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Example output below which shows getTerminalLayout info and the first recreateTerminal take a long time, the latter is quite unexpected.

Raw Perf Marks: terminal

Name	Timestamp	Delta	Total
code/terminal/willGetTerminalBackend	1726.2000000029802	0	0
code/terminal/didGetTerminalBackend	1744.1000000089407	17.900000005960464	17.900000005960464
code/terminal/willReconnect	1744.1000000089407	0	17.900000005960464
code/terminal/willGetTerminalLayoutInfo	1744.9000000059605	0.7999999970197678	18.700000002980232
code/terminal/didGetTerminalLayoutInfo	2035.2000000029802	290.29999999701977	309
code/terminal/willRecreateTerminalGroups	2035.2000000029802	0	309
code/terminal/willRecreateTerminal/5	2035.2000000029802	0	309
code/terminal/didRecreateTerminal/5	2351.6000000089407	316.40000000596046	625.4000000059605
code/terminal/willRecreateTerminal/6	2351.7000000029802	0.09999999403953552	625.5
code/terminal/didRecreateTerminal/6	2364.9000000059605	13.200000002980232	638.7000000029802
code/terminal/willRecreateTerminal/7	2366.800000011921	1.9000000059604645	640.6000000089407
code/terminal/didRecreateTerminal/7	2371.9000000059605	5.0999999940395355	645.7000000029802
code/terminal/willRecreateTerminal/8	2374.1000000089407	2.2000000029802322	647.9000000059605
code/terminal/didRecreateTerminal/8	2381.5	7.399999991059303	655.2999999970198
code/terminal/willRecreateTerminal/9	2384	2.5	657.7999999970198
code/terminal/didRecreateTerminal/9	2391.1000000089407	7.100000008940697	664.9000000059605
code/terminal/didRecreateTerminalGroups	2394.6000000089407	3.5	668.4000000059605
code/terminal/didReconnect	2396	1.3999999910593033	669.7999999970198

[jrieken]

@jrieken changes to timer service:

Changes to perf editor look good, no changes to timer service to be seen ;-)

[Tyriar]

Ah that's what I meant 😅