Release all v0.1.x crates in June 2025

[hds]

Release

Backporting / pre-work

Previous release of these crates was coordinated in #3152

• Backport everything since previous release: Backport everything up to May 2025 #3283
• Switch to main: Make crates.io branch the default branch #3294
• Backport last master PR: (backport) tracing-subscriber: count numbers of enters in Timings (#2944) #3303

Crates

• tracing-core -> v0.1.34: chore: prepare tracing-core 0.1.34 #3302 / tracing-core/0.1.34
• tracing-attributes -> v0.1.29: chore: prepare tracing-attributes 0.1.29 #3304 / tracing-attributes/0.1.29
• tracing -> v0.1.42
• tracing-subscriber -> 0.3.20
• tracing-appender -> 0.2.4

[d-e-s-o]

Are we still on track for releases by end of June? I'd be very interested in the tracing-subscriber bump. Thanks.