perf(sdk): Add regex pattern support to traces sampler route matching

[obostjancic]

Adds SAMPLED_ROUTE_PATTERNS — a list of (compiled_regex, rate) tuples — as a complement to the existing exact-match SAMPLED_ROUTES dict. traces_sampler now falls through to pattern matching when no exact route matches.

Uses this to sample all hits to the ai-conversations endpoints at 100% without hardcoding a specific org slug (a previous attempt at this used /api/0/organizations/sentry/ai-conversations/ directly, which was cleaned up in #108016).

Routes covered

# urls.py
r"^(?P<organization_id_or_slug>[^/]+)/ai-conversations/$"
r"^(?P<organization_id_or_slug>[^/]+)/ai-conversations/(?P<conversation_id>[^/]+)/$"

# sdk.py
SAMPLED_ROUTE_PATTERNS: list[tuple[re.Pattern[str], float]] = [
    (re.compile(r"^/api/0/organizations/[^/]+/ai-conversations/"), 1.0),
]